Chemical History of a Candle

Modern History Sourcebook:
Michael Faraday
The Chemical History of A Candle,

Introductory Note

Michael Faraday was the son of a blacksmith, and was born at Newington
Butts, near London, September 22, 1791. He began life as an errand boy to a
bookbinder and stationer, to whom he was later bound apprentice. After eight
years in this business, he was engaged by Sir Humphry Davy as his laboratory
assistant at the Royal Institution, and in 1813-15 he traveled extensively on
the Continent with his master, and saw some of the most famous scientists of
Europe. Shortly after his return to the Royal Institution, he began to make
contributions of his own to science, his first paper appearing in 1816. He
became director of the laboratory in 1825, and professor of chemistry in 1833;
rising rapidly, through the number and importance of his discoveries, to a
most distinguished position. But he was working at too great pressure, and in
1841 his health gave way, so that for some three years he could not work at
all. He recovered, however, and made some of his most important discoveries
after this interruption; and was offered, but declined, the presidency of both
the Royal Society and the Royal Institution. He died August 25, 1867.

It was characteristic of Faraday’s devotion to the enlargement of the
bounds of human knowledge that on his discovery of magneto-electricity he
abandoned the commercial work by which he had added to his small salary, in
order to reserve all his energies for research. This financial loss was in
part made up later by a pension of 300 pounds a year from the British

Faraday’s parents were members of the obscure religious denomination of
the Sandemanians, and Faraday himself, shortly after his marriage, at the age
of thirty, joined the same sect, to which he adhered till his death. Religion
and science he kept strictly apart, believing that the data of science were of
an entirely different nature from the direct communications between God and
the soul on which his religious faith was based.

The discoveries made by Faraday were so numerous, and often demand so
detailed a knowledge of chemistry and physics before they can be understood,
that it is impossible to attempt to describe or even enumerate them here.
Among the most important are the discovery of magneto-electric induction, of
the law of electro-chemical decomposition, of the magnetization of light, and
of diamagnetism. Round each of these are grouped numbers of derivative but
still highly important additions to scientific knowledge, and together they
form so vast an achievement as to lead his successor, Tyndall, to say, “Taking
him for all and all, I think it will be conceded that Michael Faraday was the
greatest experimental philosopher the world has ever seen; and I will add the
opinion, that the progress of future research will tend, not to dim or to
diminish, but to enhance and glorify the labours of this mighty

In spite of the highly technical nature of his work in research,
Faraday was remarkably gifted as an expounder of science to popular audiences;
and his lectures at the Royal Institution, especially those to younger
audiences, were justly famous. The following example is a classic in the
department of clear and fascinating scientific exposition.

Lecture I: A Candle: The Flame –
Its Sources – Structure Mobility – Brightness

I purpose, in return for the honor you do us by coming to see what are our
proceedings here, to bring before you, in the course of these lectures, the
Chemical History of a Candle. I have taken this subject on a former occasion,
and, were it left to my own will, I should prefer to repeat it almost every
year, so abundant is the interest that attaches itself to the subject, so
wonderful are the varieties of outlet which it offers into the various
departments of philosophy. There is not a law under which any part of this
universe is governed which does not come into play and is touched upon in
these phenomena. There is no better, there is no more open door by which you
can enter into the study of natural philosophy than by considering the
physical phenomena of a candle. I trust, therefore, I shall not disappoint you
in choosing this for my subject rather than any newer topic, which could not
be better, were it even so good.

And, before proceeding, let me say this also: that, though our subject be
so great, and our intention that of treating it honestly, seriously, and
philosophically, yet I mean to pass away from all those who are seniors among
us. I claim the privilege of speaking to juveniles as a juvenile myself. I
have done so on former occasions, and, if you please, I shall do so again.
And, though I stand here with the knowledge of having the words I utter given
to the world, yet that shall not deter me from speaking in the same familiar
way to those whom I esteem nearest to me on this occasion.

And now, my boys and girls, I must first tell you of what candles are made.
Some are great curiosities. I have here some bits of timber, branches of trees
particularly famous for their burning. And here you see a piece of that very
curious substance, taken out of some of the bogs in Ireland, called
candle-wood; a hard, strong, excellent wood, evidently fitted for good work as
a register of force, and yet, withal, burning so well that where it is found
they make splinters of it, and torches, since it burns like a candle, and
gives a very good light indeed. And in this wood we have one of the most
beautiful illustrations of the general nature of a candle that I can possibly
give. The fuel provided, the means of bringing that fuel to the place of
chemical action, the regular and gradual supply of air to that place of action
– heat and light – all produced by a little piece of wood of this kind,
forming, in fact, a natural candle.

But we must speak of candles as they are in commerce. Here are a couple of
candles commonly called dips. They are made of lengths of cotton cut off, hung
up by a loop, dipped into melted tallow, taken out again and cooled, then
redipped, until there is an accumulation of tallow round the cotton. In order
that you may have an idea of the various characters of these candles, you see
these which I hold in my hand – they are very small and very curious. They
are, or were, the candles used by the miners in coal mines. In olden times the
miner had to find his own candles, and it was supposed that a small candle
would not so soon set fire to the fire-damp in the coal mines as a large one;
and for that reason, as well as for economy’s sake, he had candles made of
this sort – 20, 30, 40, or 60 to the pound. They have been replaced since then
by the steel-mill, and then by the Davy lamp, and other safety lamps of
various kinds. I have here a candle that was taken out of the Royal George
1, it is said, by Colonel Pasley. It has been sunk in the sea for
many years, subject to the action of salt water. It shows you how well candles
may be preserved; for, though it is cracked about and broken a great deal, yet
when lighted it goes on burning regularly, and the tallow resumes its natural
condition as soon as it is fused.

[Footnote 1: The Royal George sunk at Spithead on the 29th of August,
1782. Colonel Pasley commenced operations for the removal of the wreck by
the explosion of gunpowder, in August 1839. The candle which Professor
Faraday exhibited must therefore have been exposed to the action of salt
water for upward of fifty-seven years.]

Mr. Field, of Lambeth, has supplied me abundantly with beautiful
illustrations of the candle and its materials; I shall therefore now refer to
them. And, first, there is the suet – the fat of the ox – Russian tallow, I
believe, employed in the manufacture of these dips, which Gay-Lussac, or some
one who intrusted him with his knowledge, converted into that beautiful
substance, stearin, which you see lying beside it. A candle, you know, is not
now a greasy thing like an ordinary tallow candle, but a clean thing, and you
may almost scrape off and pulverize the drops which fall from it without
soiling any thing. This is the process he adopted 2: The fat or
tallow is first boiled with quick-lime, and made into a soap, and then the
soap is decomposed by sulphuric acid, which takes away the lime, and leaves
the fat rearranged as stearic acid, while a quantity of glycerin is produced
at the same time. Glycerin – absolutely a sugar, or a substance similar to
sugar comes out of the tallow in this chemical change. The oil is then pressed
out of it; and you see here this series of pressed cakes, showing how
beautifully the impurities are carried out by the oily part as the pressure
goes on increasing, and at last you have left that substance, which is melted,
and cast into candles as here represented. The candle I have in my hand is a
stearin candle, made of stearin from tallow in the way I have told you. Then
here is a sperm candle, which comes from the purified oil of the spermaceti
whale. Here, also, are yellow beeswax and refined beeswax, from which candles
are made. Here, too, is that curious substance called paraffine, and some
paraffine candles, made of paraffine obtained from the bogs of Ireland. I have
here also a substance brought from Japan since we have forced an entrance into
that out-of-the-way place – a sort of wax which a kind friend has sent me, and
which forms a new material for the manufacture of candles.

[Footnote 2: The fat or tallow consists of a chemical combination of
fatty acids with glycerin. The lime unites with the palmitic, oleic, and
stearic acids, and separates the glycerin. After washing, the insoluble lime
soap is decomposed with hot dilute sulphuric acid. The melted fatty acids
thus rise as an oil to the surface, when they are decanted. They are again
washed and cast into thin plates, which, when cold, are placed between
layers of cocoanut matting and submitted to intense hydraulic pressure. In
this way the soft oleic acid is squeezed out, while the hard palmitic and
stearic acids remain. These are farther purified by pressure at a higher
temperature and washing in warm dilute sulphuric acid, when they are ready
to be made into candles. These acids are harder and whiter than the fats
from which they were obtained, while at the same time they are cleaner and
more combustible.]

And how are these candles made? I have told you about dips, and I will show
you how moulds are made. Let us imagine any of these candles to be made of
materials which can be cast. “Cast!” you say. “Why, a candle is a thing that
melts, and surely if you can melt it you can cast it.” Not so. It is
wonderful, in the progress of manufacture, and in the consideration of the
means best fitted to produce the required result, how things turn up which one
would not expect beforehand. Candles can not always be cast. A wax candle can
never be cast. It is made by a particular process which I can illustrate in a
minute or two, but I must not spend much time on it. Wax is a thing which,
burning so well, and melting so easily in a candle, can not be cast. However,
let us take a material that can be cast. Here is a frame, with a number of
moulds fastened in it. The first thing to be done is to put a wick through
them. Here is one – a plaited wick, which does not require snuffing
3 supported by a little wire. It goes to the bottom, where it is
pegged in – the little peg holding the cotton tight, and stopping the aperture
so that nothing fluid shall run out. At the upper part there is a little bar
placed across, which stretches the cotton and holds it in the mould. The
tallow is then melted, and the moulds are filled. After a certain time, when
the moulds are cool, the excess of tallow is poured off at one corner, and
then cleaned off altogether, and the ends of the wick cut away. The candles
alone then remain in the mould, and you have only to upset them, as I am
doing, when out they tumble, for the candles are made in the form of cones,
being narrower at the top than at the bottom: so that, what with their form
and their own shrinking, they only need a little shaking, and out they fall.
In the same way are made these candles of stearin and of paraffine. It is a
curious thing to see how wax candles are made. A lot of cottons are hung upon
frames, as you see here, and covered with metal tags at the ends to keep the
wax from covering the cotton in those places. These are carried to a heater,
where the wax is melted. As you see, the frames can turn round; and, as they
turn, a man takes a vessel of wax and pours it first down one, and then the
next, and the next, and so on. When he has gone once round, if it is
sufficiently cool, he gives the first a second coat, and so on until they are
all of the required thickness. When they have been thus clothed, or fed, or
made up to that thickness, they are taken off and placed elsewhere. I have
here, by the kindness of Mr. Field, several specimens of these candles. Here
is one only half-finished. They are then taken down and well rolled upon a
fine stone slab, and the conical top is moulded by properly shaped tubes, and
the bottoms cut off and trimmed. This is done so beautifully that they can
make candles in this way weighing exactly four or six to the pound, or any
number they please.

[Footnote 3: A little borax or phosphorus salt is sometime added in order
to make the ash fusible.]

We must not, however, take up more time about the mere manufacture, but go
a little farther into the matter. I have not yet referred you to luxuries in
candles (for there is such a thing as luxury in candles). See how beautifully
these are colored; you see here mauve, magenta, and all the chemical colors
recently introduced, applied to candles. You observe, also, different forms
employed. Here is a fluted pillar most beautifully shaped; and I have also
here some candles sent me by Mr. Pearsall, which are ornamented with designs
upon them, so that, as they burn, you have, as it were, a glowing sun above,
and bouquet of flowers beneath. All, however, that is fine and beautiful is
not useful. These fluted candles, pretty as they are, are bad candles; they
are bad because of their external shape. Nevertheless, I show you these
specimens, sent to me from kind friends on all sides, that you may see what is
done and what may be done in this or that direction; although, as I have said,
when we come to these refinements, we are obliged to sacrifice a little in

Now as to the light of the candle. We will light one or two, and set them
at work in the performance of their proper functions. You observe a candle is
a very different thing from a lamp. With a lamp you take a little oil, fill
your vessel, put in a little moss or some cotton prepared by artificial means,
and then light the top of the wick. When the flame runs down the cotton to the
oil, it gets extinguished, but it goes on burning in the part above. Now I
have no doubt you will ask how it is that the oil which will not burn of
itself gets up to the top of the cotton, where it will burn. We shall
presently examine that; but there is a much more wonderful thing about the
burning of a candle than this. You have here a solid substance with no vessel
to contain it; and how is it that this solid substance can get up to the place
where the flame is? How is it that this solid gets there, it not being a
fluid? or, when it is made a fluid, then how is it that it keeps together?
This is a wonderful thing about a candle.

We have here a good deal of wind, which will help us in some of our
illustrations, but tease us in others; for the sake, therefore, of a little
regularity, and to simplify the matter, I shall make a quiet flame, for who
can study a subject when there are difficulties in the way not belonging to
it? Here is a clever invention of some costermonger or street-stander in the
market-place for the shading of their candles on Saturday nights, when they
are selling their greens, or potatoes, or fish. I have very often admired it.
They put a lamp-glass round the candle, supported on a kind of gallery, which
clasps it, and it can be slipped up and down as required. By the use of this
lamp-glass, employed in the same way, you have a steady flame, which you can
look at, and carefully examine, as I hope you will do, at home.

You see, then, in the first instance, that a beautiful cup is formed. As
the air comes to the candle, it moves upward by the force of the current which
the heat of the candle produces, and it so cools all the sides of the wax,
tallow, or fuel as to keep the edge much cooler than the part within; the part
within melts by the flame that runs down the wick as far as it can go before
it is extinguished, but the part on the outside does not melt. If I made a
current in one direction, my cup would be lop-sided, and the fluid would
consequently run over; for the same force of gravity which holds worlds
together holds this fluid in a horizontal position, and if the cup be not
horizontal, of course the fluid will run away in guttering. You see,
therefore, that the cup is formed by this beautifully regular ascending
current of air playing upon all sides, which keeps the exterior of the candle
cool. No fuel would serve for a candle which has not the property of giving
this cup, except such fuel as the Irish bogwood, where the material itself is
like a sponge and holds its own fuel. You see now why you would have had such
a bad result if you were to burn these beautiful candles that I have shown
you, which are irregular, intermittent in their shape, and can not, therefore,
have that nicely-formed edge to the cup which is the great beauty in a candle.
I hope you will now see that the perfection of a process – that is, its
utility – is the better point of beauty about it. It is not the gest looking
thing, but the best acting thing, which is the most advantageous to us. This
good-looking candle is a bad-burning one. There will be a guttering round
about it because of the irregularity of the stream of air and the badness of
the cup which is formed thereby. You may see some pretty examples (and I trust
you will notice these instances) of the action of the ascending current when
you have a little gutter run down the side of a candle, making it thicker
there than it is elsewhere. As the candle goes on burning, that keeps its
place and forms a little pillar sticking up by the side, because, as it rises
higher above the rest of the wax or fuel, the air gets better round it, and it
is more cooled and better able to resist the action of the heat at a little
distance. Now the greatest mistakes and faults with regard to candles, as in
many other things, often bring with them instruction which we should not
receive if they had not occurred. We come here to be philosophers, and I hope
you will always remember that whenever a result happens, especially if it be
new, you should say, “What is the cause? Why does it occur?” and you will, in
the course of time, find out the reason.

Then there is another point about these candles which will answer a
question – that is, as to the way in which this fluid gets out of the cup, up
the wick, and into the place of combustion. You know that the flames on these
burning wicks in candles made of beeswax, stearin, or spermaceti, do not run
down to the wax or other matter, and melt it all away, but keep to their own
right place. They are fenced off from the fluid below, and do not encroach on
the cup at the sides. I can not imagine a more beautiful example than the
condition of adjustment under which a candle makes one part subserve to the
other to the very end of its action. A combustible thing like that, burning
away gradually, never being intruded upon by the flame, is a very beautiful
sight, especially when you come to learn what a vigorous thing flame is – what
power it has of destroying the wax itself when it gets hold of it, and of
disturbing its proper form if it come only too near.

But how does the flame get hold of the fuel? There is a beautiful point
about that – capillary attraction. 4 “Capillary attraction!” you
say – “the attraction of hairs.” Well, never mind the name; it was given in
old times, before we had a good understanding of what the real power was. It
is by what is called capillary attraction that the fuel is conveyed to the
part where combustion goes on, and is deposited there, not in a careless way,
but very beautifully in the very midst of the centre of action, which takes
place around it. Now I am going to give you one or two instances of capillary
attraction. It is that kind of action or attraction which makes two things
that do not dissolve in each other still hold together. When you wash your
hands, you wet them thoroughly; you take a little soap to make the adhesion
better, and you find your hands remain wet. This is by that kind of attraction
of which I am about to speak. And, what is more, if your hands are not soiled
(as they almost always are by the usages of life), if you put your finger into
a little warm water, the water will creep a little way up the finger, though
you may not stop to examine it. I have here a substance which is rather porous
– a column of salt – and I will pour into the plate at the bottom, not water,
as it appears, but a saturated solution of salt which can not absorb more, so
that the action which you see will not be due to its dissolving any thing. We
may consider the plate to be the candle, and the salt the wick, and this
solution the melted tallow. (I have colored the fluid, that you may see the
action better.) You observe that, now I pour in the fluid, it rises and
gradually creeps up the salt higher and higher; and provided the column does
not tumble over, it will go to the top. If this blue solution were
combustible, and we were to place a wick at the top of the salt, it would burn
as it entered into the wick. It is a most curious thing to see this kind of
action taking place, and to observe how singular some of the circumstances are
about it. When you wash your hands, you take a towel to wipe off the water;
and it is by that kind of wetting, or that kind of attraction which makes the
towel become wet with water, that the wick is made wet with the tallow. I have
known some careless boys and girls (indeed, I have known it happen to careful
people as well) who, having washed their hands and wiped them with a towel,
have thrown the towel over the side of the basin, and before long it has drawn
all the water out of the basin and conveyed it to the floor, because it
happened to be thrown over the side in such a way as to serve the purpose of a
siphon. 5 That you may the better see the way in which the
substances act one upon another, I have here a vessel made of wire gauze
filled with water, and you may compare it in its action to the cotton in one
respect, or to a piece of calico in the other. In fact, wicks are sometimes
made of a kind of wire gauze. You will observe that this vessel is a porous
thing; for if I pour a little water on to the top, it will run out at the
bottom. You would be puzzled for a good while if I asked you what the state of
this vessel is, what is inside it, and why it is there? The vessels is full of
water, and yet you see the water goes in and runs out as if it were empty. In
order to prove this to you, I have only to empty it. The reason is this: the
wire, being once wetted, remains wet; the meshes are so small that the fluid
is attracted so strongly from the one side to the other, as to remain in the
vessel, although it is porous. In like manner, the particles of melted tallow
ascend the cotton and get to the top: other particles then follow by their
mutual attraction for each other, and as they reach the flame they are
gradually burned.

[Footnote 4: Capillary attraction or repulsion is the cause which
determines the ascent or descent of a fluid in a capillary tube. If a piece
of thermometer tubing, open at each end, be plunged into water, the latter
will instantly rise in the tube considerably above its external level. If,
on the other hand, the tube be plunged into mercury, a repulsion instead of
attraction will be exhibited, and the level of the mercury will be lower in
the tube than it is outside.]

[Footnote 5: The late Duke of Sussex was, we believe, the first to show
that a prawn might be washed upon this principle. If the tail, after pulling
off the fan part, be placed in a tumbler of water, and the head be allowed
to hang over the outside, the water will be sucked up the tail by capillary
attraction, and will continue to run out through the head until the water in
the glass has sunk so low the tail ceases to dip into it.]

Here is another application of the same principle. You see this bit of
cane. I have seen boys about the streets, who are very anxious to appear like
men, take a piece of cane, and light it, and smoke it, as an imitation of a
cigar. They are enable to do so by the permeability of the cane in one
direction, and by its capillarity. If I place this piece of cane on a plate
containing some camphene (which is very much like paraffine in its general
character), exactly in the same manner as the blue fluid rose through the salt
will this fluid rise through the piece of cane. There being no pores at the
side, the fluid can not go in that direction, but must pass through its
length. Already the fluid is at the top of the cane; now I can light it and
make it serve as a candle. The fluid has risen by the capillary attraction of
the piece of cane, just as it does through the cotton in the candle.

Now the only reason why the candle does not burn all down the side of the
wick is that the melted tallow extinguishes the flame. You know that a candle,
if turned upside down, so as to allow the fuel to run upon the wick, will be
put out. The reason is, that the flame has not had time to make the fuel hot
enough to burn, as it does above, where it is carried in small quantities into
the wick, and has all the effect of the heat exercised upon it.

There is another condition which you must learn as regards the candle,
without which you would not be able fully to understand the philosophy of it,
and that is the vaporous condition of the fuel. In order that you may
understand that, let me show you a very pretty but very commonplace
experiment. If you blow a candle out cleverly, you will see the vapor rise
from it. You have, I know, often smelt the vapor of a blown-out candle, and a
very bad smell it is; but if you blow it out cleverly you will be able to see
pretty well the vapor into which this solid matter is transformed. I will blow
out one of these candles in such a way as not to disturb the air around it by
the continuing action of my breath; and now, if I hold a lighted taper two or
three inches from the wick, you will observe a train of fire going through the
air till it reaches the candle. I am obliged to be quick and ready, because if
I allow the vapor time to cool, it becomes condensed into a liquid or solid,
or the stream of combustible matter gets disturbed.

Now as to the shape or form of the flame. It concerns us much to know about
the condition which the matter of the candle finally assumes at the top of the
wick, where you have such beauty and brightness as nothing but combustion or
flame can produce. You have the glittering beauty of gold and silver, and the
still higher lustre of jewels like the ruby and diamond; but none of these
rival the brilliancy and beauty of flame. What diamond can shine like flame?
It owes its lustre at nighttime to the very flame shining upon it. The flame
shines in darkness, but the light which the diamond has is as nothing until
the flame shines upon it, when it is brilliant again. The candle alone shines
by itself and for itself, or for those who have arranged the materials. Now
let us look a little at the form of the flame as you see it under the glass
shade. It is steady and equal, and its general form is that which is
represented in the diagram, varying with atmospheric disturbances, and also
varying according to the size of the candle. It is a bright oblong, brighter
at the top than toward the bottom, with the wick in the middle, and, besides
the wick in the middle, certain darker parts towards the bottom, where the
ignition is not so perfect as in the part above. I have a drawing here,
sketched many years ago by Hooker, when he made his investigations. It is the
drawing of the flame of a lamp, but it will apply to the flame of a candle.
The cup of the candle is the vessel or lamp; the melted spermaceti is the oil;
and the wick is common to both. Upon that he sets this little flame, and then
he represents what is true, a certain quantity of matter rising about it which
you do not see, and which, if you have not been here before, or are not
familiar with the subject, you will not know of. He has here represented the
parts of the surrounding atmosphere that are very essential to the flame, and
that are always present with it. There is a current formed, which draws the
flame out; for the flame which you see is really drawn out by the current, and
drawn upward to a great height, just as Hooker has here shown you by that
prolongation of the current in the diagram. You may see this by taking a
lighted candle, and putting it in the sun so as to get its shadow thrown on a
piece of paper. How remarkable it is that that thing which is light enough to
produce shadows of other objects can be made to throw its own shadow on a
piece of white paper or card, so that you can actually see streaming round the
flame something which is not part of the flame, but is ascending and drawing
the flame upward. Now I am going to imitate the sunlight by applying the
voltaic battery to the electric lamp. You now see our sun and its great
luminosity; and by placing a candle between it and the screen, we get the
shadow of the flame. You observe the shadow of the candle and of the wick;
then there is a darkish part, as represented in the diagram, and then a part
which is more distinct. Curiously enough, however, what we see in the shadow
as the darkest part of the flame is, in reality, the brightest part; and here
you see streaming upward the ascending current of hot air, as shown by Hooker,
which draws out the flame, supplies it with air, and cools the sides of the
cup of melted fuel.

I can give you here a little farther illustration, for the purpose of
showing you how flame goes up or down according to the current. I have here a
flame – it is not a candle flame – but you can, no doubt, by this time
generalize enough to be able to compare one thing with another. What I am
about to do is to change the ascending current that takes the flame upward
into a descending current. This I can easily do by the little apparatus you
see before me. The flame, as I have said, is not a candle flame, but it is
produced by alcohol, so that it shall not smoke too much. I will also color
the flame with another substance 6, so that you may trace its
course; for, with the spirit alone, you could hardly see well enough to have
the opportunity of tracing its direction. By lighting this spirit of wine we
have then a flame produced, and you observe that when held in the air it
naturally goes upward. You understand now, easily enough, why flames go up
under ordinary circumstances: it is because of the draught of air by which the
combustion is formed. But now, by blowing the flame down, you see I am enabled
to make it go downward into this little chimney, the direction of the current
being changed. Before we have concluded this course of lectures we shall show
you a lamp in which the flame goes up and the smoke goes down, or the flame
goes down and the smoke goes up. You see, then, that we have the power in this
way of varying the flame in different directions.

[Footnote 6: The alcohol had chloride of copper dissolved in it: this
produces a beautiful green flame.]

There are now some other points that I must bring before you. Many of the
flames you see here vary very much in their shape by the currents of air
blowing around them in different directions; but we can, if we like, make
flames so that they will look like fixtures, and we can photograph them
indeed, we have to photograph them – so that they become fixed to us, if we
wish to find out every thing concerning them. That, however, is not the only
thing I wish to mention. If I take a flame sufficiently large, it does not
keep that homogeneous, that uniform condition of shape, but it breaks out with
a power of life which is quite wonderful. I am about to use another kind of
fuel, but one which is truly and fairly a representative of the wax or tallow
of a candle. I have here a large ball of cotton, which will serve as a wick.
And, now that I have immersed it in spirit and applied a light to it, in what
way does it differ from an ordinary candle? Why, it differs very much in one
respect, that we have a vivacity and power about it, a beauty and a life
entirely different from the light presented by a candle. You see those fine
tongues of flame rising up. You have the same general disposition of the mass
of the flame from below upward; but, in addition to that, you have this
remarkable breaking out into tongues which you do not perceive in the case of
a candle. Now, why is this? I must explain it to you, because, when you
understand that perfectly, you will be able to follow me better in what I have
to say hereafter. I suppose some here will have made for themselves the
experiment I am going to show you. Am I right in supposing that any body here
has played at snapdragon? I do not know a more beautiful illustration of the
philosophy of flame, as to a certain part of its history, than the game of
snapdragon. First, here is the dish; and let me say, that when you play
snapdragon properly you ought to have the dish well warmed; you ought also to
have warm plums, and warm brandy, which, however, I have not got. When you
have put the spirit into the dish, you have the cup and the fuel; and are not
the raisins acting like the wicks? I now throw the plums into the dish, and
light the spirit, and you see those beautiful tongues of flame that I refer
to. You have the air creeping in over the edge of the dish forming these
tongues. Why? Because, through the force of the current and the irregularity
of the action of the flame, it can not flow in one uniform stream. The air
flows in so irregularly that you have what would otherwise be a single image
broken up into a variety of forms, and each of these little tongues has an
independent existence of its own. Indeed, I might say, you have here a
multitude of independent candles. You must not imagine, because you see these
tongues all at once, that the flame is of this particular shape. A flame of
that shape is never so at any one time. Never is a body of flame, like that
which you just saw rising from the ball, of the shape it appears to you. I
consists of a multitude of different shapes, succeeding each other so fast
that the eye is only able to take cognizance of them all at once. In former
times I purposely analyzed a flame of that general character, and the diagram
shows you the different parts of which it is composed. They do not occur all
at once; it is only because we see these shapes in such rapid succession that
they seem to us to exist all at one time.

It is too bad that we have not got farther than my game of snapdragon; but
we must not, under any circumstances, keep you beyond your time. It will be a
lesson to me in future to hold you more strictly to the philosophy of the
thing than to take up your time so much with these illustrations.

Lecture II: Brightness Of
The Flame – Air Necessary For Combustion – Production Of

We were occupied the last time we met in considering the general character
and arrangement as regards the fluid portion of a candle, and the way in which
that fluid got into the place of combustion. You see, when we have a candle
burning fairly in a regular, steady atmosphere, it will have a shape something
like the one shown in the diagram, and will look pretty uniform, although very
curious in its character. And now I have to ask your attention to the means by
which we are enabled to ascertain what happens in any particular part of the
flame; why it happens; what it does in happening; and where, after all, the
whole candle goes to; because, as you know very well, a candle being brought
before us and burned, disappears, if burned properly, without the least trace
of dirt in the candle stick, and this is a very curious circumstance. In
order, then, to examine this candle carefully, I have arranged certain
apparatus, the use of which you will see as I go on. Here is a candle; I am
about to put the end of this glass tube into the middle of the flame – into
that part which old Hooker has represented in the diagram as being rather
dark, and which you can see at any time if you will look at a candle
carefully, without blowing it about. We will examine this dark part first.

Now I take this bent glass tube, and introduce one end into that part of
the flame, and you see at once that something is coming from the flame, out at
the other end of the tube; and if I put a flask there, and leave it for a
little while, you will see that something from the middle part of the flame is
gradually drawn out, and goes through the tube, and into that flask, and there
behaves very differently from what it does in the open air. It not only
escapes from the end of the tube, but falls down to the bottom of the flask
like a heavy substance, as indeed it is. We find that this is the wax of
experiment, if there is not too much disturbance, there will always be a ring.
This is a good experiment for you to make at home. Take a strip of paper, have
the air in the room quiet, and put the piece of paper right across the middle
of the flame – (I must not talk while I make the experiment) – and you will
find that it is burnt in two places, and that it is not burnt, or very little
so, in the middle; and when you have tried the experiment once or twice, so as
to make it nicely, you will be very interested to see where the heat is, and
to find that it is where the air and the fuel come together.

This is most important for us as we proceed with out subject. Air is
absolutely necessary for combustion; and, what is more, I must have you
understand that fresh air is necessary, or else we should be imperfect in our
reasoning and our experiments. Here is a jar of air; I place it over a candle,
and it burns very nicely in it at first, showing that what I have said about
it is true; but there will soon be a change. See how the flame is drawing
upward, presently fading, and at last going out. And going out, why? Not
because it wants air merely, for the jar is as full now as it was before; but
it wants pure, fresh air. The jar is full of air, partly changed, partly not
changed; but it does not contain sufficient of the fresh air which is
necessary for the combustion of a candle. These are all points which we, as
young chemists, have to gather up; and if we look a little more closely into
this kind of action, we shall find certain steps of reasoning extremely
interesting. For instance, here is the oil-lamp I showed you – an excellent
lamp for our experiments – the old Argand lamp. I now make it like a candle
(obstructing the passage of air into the centre of the flame); there is the
cotton; there is the oil rising up in it, and there is the conical flame. It
burns poorly because there is a partial restraint of air. I have allowed no
air to get to it save around the outside of the flame, and it does not burn
well. I can not admit more air from the outside, because the wick is large;
but if, as Argand did so cleverly, I open a passage to the middle of the
flame, and so let air come in there, you will see how much more beautifully it
burns. If I shut the air off, look how it smokes; and why? We have now some
very interesting points to study: we have the case of the combustion of a
candle; we have the case of a candle being put out by the want of air; and we
have now the case of imperfect combustion, and this is to us so interesting
that I want you to understand it as thoroughly as you do the case of a candle
burning in its best possible manner. I will now make a great flame, because we
need the largest possible illustrations. Here is a larger wick (burning
turpentine on a ball of cotton). All these things are the same as candles,
after all. If we have larger wicks, we must have a larger supply of air, or we
shall have less perfect combustion. Look, now, at this black substance going
up into the atmosphere; there is a regular stream of it. I have provided means
to carry off the imperfectly burned part, lest it should annoy you. Look at
the soots that fly off from the flame; see what an imperfect combustion it is,
because it can not get enough air. What, then, is happening? Why, certain
things which are necessary to the combustion of a candle are absent, and very
bad results are accordingly produced; but we see what happens to a candle when
it is burnt in a pure and proper state of air. At the time when I showed you
this charring by the ring of flame on the one side of the paper, I might have
also shown you, by turning to the other side, that the burning of a candle
produces the same kind of soot – charcoal, or carbon.

But, before I show that, let me explain to you, as it is quite necessary
for our purpose, that, though I take a candle, and give you, as the general
result, its combustion in the form of a flame, we must see whether combustion
is always in this condition, or whether there are other conditions of flame;
and we shall soon discover that there are, and that they are most important to
us. I think, perhaps, the best illustration of such a point to us, as
juveniles, is to show the result of strong contrast. Here is a little
gunpowder. You know that gunpowder burns with flame; we may fairly call it
flame. It contains carbon and other materials, which altogether cause it to
burn with a flame. And here is some pulverized iron, or iron filings. Now I
purpose burning these two things together. I have a little mortar in which I
will mix them. (Before I go into these experiments, let me hope that none of
you, by trying to repeat them for fun’s sake, will do any harm. These things
may all be very properly used if you take care, but without that much mischief
will be done.) Well, then here is a little gunpowder, which I put at the
bottom of that little wooden vessel, and mix the iron filings up with it, my
object being to make the gunpowder set fire to the filings and burn them in
the air, and thereby show the difference between substances burning with flame
and not with flame. Here is the mixture; and when I set fire to it you must
watch the combustion, and you will see that it is of two kinds. You will see
the gunpowder burning with a flame and the filings thrown up. You will see
them burning, too, but without the production of flame. They will each burn
separately. [The lecturer then ignited the mixture.] There is the gunpowder,
which burns with a flame, and there are the filings: they burn with a
different kind of combustion. You see, then, these two great distinctions; and
upon these differences depend all the utility and all the beauty of flame
which we use for the purpose of giving out light. When we use oil, or gas, or
candle for the purpose of illumination, their fitness all depends upon these
different kinds of combustion.

There are such curious conditions of flame that it requires some cleverness
and nicety of discrimination to distinguish the kinds of combustion one from
another. For instance, here is a powder which is very combustible, consisting,
as you see, of separate little particles. It is called lycopodium,
7 and each of these particles can produce a vapor, and produce its
own flame; but, to see them burning, you would imagine it was all one flame. I
will now set fire to a quantity, and you will see the effect. We saw a cloud
of flame, apparently in one body; but that rushing noise [referring to the
sound produced by the burning] was a proof that the combustion was not a
continuous or regular one. This is the lightning of the pantomimes, and a very
good imitation. [The experiment was twice repeated by blowing lycopodium from
a glass tube through a spirit flame.] This is not an example of combustion
like that of the filings I have been speaking of, to which we must now

[Footnote 7: Lycopodium is a yellowish powder found in the fruit of the
club moss (Lycopodium clavatum). It is used in fireworks.]

Suppose I take a candle and examine that part of it which appears brightest
to our eyes. Why, there I get these black particles, which already you have
seen many times evolved from the flame, and which I am now about to evolve in
a different way. I will take this candle and clear away the gutterage, which
occurs by reason of the currents of air, and if I now arrange the glass tube
so as just to dip into this luminous part, as in our first experiment, only
higher, you see the result. In place of having the same white vapor that you
had before, you will now have a black vapor. There is goes, as black as ink.
It is certainly very different from the white vapor; and when we put a light
to it we shall find that it does not burn, but that it puts the light out.
Well, these particles, as I said before, are just the smoke of the candle; and
this brings to mind that old employment which Dean Swift recommended to
servants for their amusement, namely writing on the ceiling of a room with a
candle. But what is that black substance? Why, it is the same carbon which
exists in the candle. How comes it out of the candle? It evidently existed in
the candle, or else we should not have had it here. And now I want you to
follow me in this explanation. You would hardly think that all those
substances which fly about London, in the form of soots and blacks, are the
very beauty and life of the flame, and which are burned in it as those iron
filings were burned here. Here is a piece of wire gauze, which will not let
the flame go through it; and I think you will see, almost immediately, that
when I bring it low enough to touch that part of the flame which is otherwise
so bright, it quells and quinches it at once, and allows a volume of smoke to
rise up.

I want you now to follow me in this point – that whenever a substance
burns, as the iron filings burnt in the flame of gunpowder, without assuming
the vaporous state (whether it becomes liquid or remains solid), it becomes
exceedingly luminous. I have here taken three or four examples apart from the
candle on purpose to illustrate this point to you, because what I have to say
is applicable to all substances, whether they burn or whether they do not burn
– that they are exceedingly bright if they retain their solid state, and that
it is to this presence of solid particles in the candle flame that it owes its

Here is a platinum wire, a body which does not change by heat. If I heat it
in this flame, see how exceedingly luminous it becomes. I will make the flame
dim for the purpose of giving a little light only, and yet you will see that
the heat which it can give to that platinum wire, though far less than the
heat it has itself, is able to raise the platinum wire to a far higher state
of effulgence. This flame has carbon in it; but I will take one that has no
carbon in it. There is a material, a kind of fuel – a vapor, or gas, whichever
you like to call it – in that vessel, and it has no solid particles in it; so
I take that because it is an example of flame itself burning without any solid
matter whatever; and if I now put this solid substance in it, you see what an
intense heat it has, and how brightly it causes the solid body to glow. This
is the pipe through which we convey this particular gas, which we call
hydrogen, and which you shall know all about the next time we meet. And here
is a substance called oxygen, by means of which this hydrogen can burn; and
although we produce, by their mixture, far greater heat 8 than you
can obtain from the candle, yet there is very little light. If, however, I
take a solid substance, and put that into it, we produce an intense light. If
I take a piece of lime, a substance which will not burn, and which will not
vaporize by the heat (and because it does not vaporize remains solid, and
remains heated), you will soon observe what happens as to its glowing. I have
here a most intense heat produced by the burning of hydrogen in contact with
the oxygen; but there is as yet very little light – not for want of heat, but
for want of particles which can retain their solid state; but when I hold this
piece of lime in the flame of the hydrogen as it burns in the oxygen, see how
it glows! This is glorious lime light, which rivals the voltaic light, and
which is almost equal to sunlight. I have here a piece of carbon or charcoal,
which will burn and give us light exactly in the same manner as if it were
burnt as part of a candle. The heat that is in the flame of a candle
decomposes the vapor of the wax, and sets free the carbon particles; they rise
up heated and glowing as this now glows, and then enter into the air. But the
particles, when burnt, never pass off from a candle in the form of carbon.
They go off into the air as a perfectly invisible substance, about which we
shall know hereafter.

[Footnote 8: Bunsen has calculated that the temperature of the
oxyhydrogen blowpipe is 8061C. Hydrogen burning in air has a temperature of
3259C., and coal gas in air, 2350C]

Is it not beautiful to think that such a process is going on, and that such
a dirty things as charcoal can become so incandescent? You see it comes to
this – that all bright flames contain these solid particles; all things that
burn and produce solid particles, either during the time they are burning, as
in the candle, or immediately after being burnt, as in the case of the
gunpowder and iron filings – all these things give us this glorious and
beautiful light.

I will give you a few illustrations. Here is a piece of phosphorus, which
burns with a bright flame. Very well; we may now conclude that phosphorus will
produce, either at the moment that it is burning or afterwards, these solid
particles. Here is the phosphorus lighted, and I cover it over with this glass
for the purpose of keeping in what is produced. What is all that smoke? That
smoke consists of those very particles which are produced by the combustion of
the phosphorus. Here, again, are two substances. This is chlorate of potassa,
and this other sulphuret of antimony. I shall mix these together a little, and
then they may be burnt in many ways. I shall touch them with a drop of
sulphuric acid, for the purpose of giving you an illustration of chemical
action, and they will instantly burn. 9 [The lecturer then ignited
the mixture by means of sulphuric acid.] Now, from the appearance of things,
you can judge for yourselves whether they produce solid matter in burning. I
have given you the train of reasoning which will enable you to say whether
they do or do not; for what is this bright flame but the solid particles
passing off?

[Footnote 9: The following is the action of the sulphuric in inflaming
the mixture of sulphuret of antimony and chlorate of potassa. A portion of
the latter is decomposed by the sulphuric acid into oxide of chlorine,
bisulphate of potassa, and perchlorate of potassa. The oxide of chlorine
inflames the sulphuret of antimony, which is a combustible body, and the
whole mass instantly bursts into flame.]

Mr. Anderson has in the furnace a very hot crucible. I am about to throw
into it some zinc filings, and they will burn with flame like gunpowder. I
make this experiment because you can make it well at home. Now I want you to
see what will be the result of the combustion of this zinc. Here it is burning
– burning beautifully like a candle, I may say. But what is all that smoke,
and what are those little clouds of wool which will come to you if you can not
come to them, and make themselves sensible to you in the form of the old
philosophic wool, as it was called? We shall have left in that crucible, also,
a quantity of this woolly matter. But I will take a piece of this same zinc,
and make an experiment a little more closely at home, as it were. You will
have here the same thing happening. Here is the piece of zinc; there [pointing
to a jet of hydrogen] is the furnace, and we will set to work and try and burn
the metal. It glows, you see; there is the combustion; and there is the white
substance into which it burns. And so, if I take that flame of hydrogen as the
representative of a candle, and show you a substance like zinc burning in the
flame, you will see that it was merely during the action of combustion that
this substance glowed – while it was kept hot; and if I take a flame of
hydrogen and put this white substance from the zinc into it, look how
beautifully it glows, and just because it is a solid substance.

I will now take such a flame as I had a moment since, and set free from it
the particles of carbon. Here is some camphene, which will burn with a smoke;
but if I send these particles of smoke through this pipe into the hydrogen
flame you will see they will burn and become luminous, because we heat them a
second time. There they are. Those are the particles of carbon reignited a
second time. They are those particles which you can easily see by holding a
piece of paper behind them, and which, while they are in the flame, are
ignited by the heat produced, and, when so ignited, produce this brightness.
When the particles are not separated you get no brightness. The flame of coal
gas owes its brightness to the separation, during combustion, of these
particles of carbon, which are equally in that as in a candle. I can very
quickly alter that arrangement. Here, for instance is a bright flame of gas.
Supposing I add so much air to the flame as to cause it all to burn before
those particles are set free, I shall not have this brightness; and I can do
that in this way: If I place over the jet this wire-gauze cap, as you see, and
then light the gas over it, it burns with a non-luminous flame, owing to its
having plenty of air mixed with it before it burns; and if I raise the gauze,
you see it does not burn below 10. There is plenty of carbon in the
gas; but, because the atmosphere can get to it, and mix with it before it
burns, you see how pale and blue the flame is. And if I blow upon a bright gas
flame, so as to consume all this carbon before it gets heated to the glowing
point, it will also burn blue. [The lecturer illustrated his remarks by
blowing on the gas light.] The only reason why I have not the same bright
light when I thus blow upon the flame is that the carbon meets with sufficient
air to burn it before it gets separated in the flame in a free state. The
difference is solely due to the solid particles not being separated before the
gas is burnt.

[Footnote 10: The “air-burner,” which is of such value in the laboratory,
owes its advantage to this principle. It consists of a cylindrical metal
chimney, covered at the top with a piece of rather coarse iron wire gauze.
This is supported over an Argand burner in such a manner that the gas may
mix in the chimney with an amount of air sufficient to burn the carbon and
hydrogen simultaneously, so that there may be no separation of carbon in the
flame with consequent deposition of soot. The flame, being unable to pass
through the wire gauze, burns in a steady, nearly invisible manner

You observe that there are certain products as the result of the combustion
of a candle, and that of these products one portion may be considered as
charcoal, or soot; that charcoal, when afterward burnt, produces some other
product; and it concerns us very much now to ascertain what that other product
is. We showed that something was going away; and I want you now to understand
how much is going up into the air; and for that purpose we will have
combustion on a little larger scale. From that candle ascends heated air, and
two or three experiments will show you the ascending current; but, in order to
give you a notion of the quantity of matter which ascends in this way, I will
make an experiment by which I shall try to imprison some of the products of
this combustion. For this purpose I have here what boys call a fire-balloon; I
use this fire-balloon merely as a sort of measure of the result of the
combustion we are considering; and I am about to make a flame in such an easy
and simple manner as shall best serve my present purpose. This plate shall be
the “cup,” we will so say, of the candle; this spirit shall be our fuel; and I
am about to place this chimney over it, because it is better for me to do so
than to let things proceed at random. Mr. Anderson will now light the fuel,
and here at the top we shall get the results of the combustion. What we get at
the top of that tube is exactly the same, generally speaking, as you get from
the combustion of a candle; but we do not get a luminous flame here, because
we use a substance which is feeble in carbon. I am about to put this balloon –
not into action, because that is not my object – but to show you the effect
which results from the action of those products which arise from the candle,
as they arise here from the furnace. [The balloon was held over the chimney,
when it immediately commenced to fill.] You see how it is disposed to ascend;
but we must not let it up; because it might come in contact with those upper
gaslights, and that would be very inconvenient. [The upper gaslights were
turned out at the request of the lecturer, and the balloon was allowed to
ascend.] Does not that show you what a large bulk of matter is being evolved?
Now there is going through this tube [placing a large glass tube over a
candle] all the products of that candle, and you will presently see that the
tube will become quite opaque. Suppose I take another candle, and place it
under a jar, and then put a light on the other side, just to show you what is
going on. You see that the sides of the jar become cloudy, and the light
begins to burn feebly. It is the products, you see, which make the light so
dim, and this is the same thing which makes the sides of the jar so opaque. If
you go home, and take a spoon that has been in the cold air, and hold it over
a candle – not so as to soot it – you will find that it becomes dim just as
that jar is dim. If you can get a silver dish, or something of that kind, you
will make the experiment still better; and now, just to carry your thoughts
forward to the time we shall next meet, let me tell you that it is water which
causes the dimness, and when we next meet I will show that we can make it,
without difficulty, assume the form of a liquid.

Lecture III: Products:
Water From The Combustion – Nature Of Water – A Compound –

I Dare say you well remember that when we parted we had just mentioned the
word “products” from the candle; for when a candle burns we found we were
able, by nice adjustment, to get various products from it. There was one
substance which was not obtained when the candle was burning properly, which
was charcoal or smoke, and there was some other substance that went upward
from the flame which did not appear as smoke, but took some other form, and
made part of that general current which, ascending from the candle upward,
becomes invisible, and escapes. There were also other products to mention. You
remember that in that rising current having its origin at the candle we found
that one part was condensable against a cold spoon, or against a clean plate,
or any other cold thing, and another part was incondensable.

We will first take the condensable part, and examine it, and, strange to
say, we find that that part of the product is just water – nothing but water.
On the last occasion I spoke of it incidentally, merely saying that water was
produced among the condensable products of the candle; but to-day I wish to
draw your attention to water, that we may examine it carefully, especially in
relation to this subject, and also with respect to its general existence on
the surface of the globe.

Now, having previously arranged an experiment for the purpose of condensing
water from the products of the candle, my next point will be to show you this
water; and perhaps one of the best means that I can adopt for showing its
presence to so many at once is to exhibit a very visible action of water and
then to apply that test to what is collected as a drop at the bottom of that
vessel. I have here a chemical substance, discovered by Sir Humphry Davy,
which has a very energetic action upon water, which I shall use as a test of
the presence of water. If I take a little piece of it – it is called
potassium, as coming from potash – if I take a little piece of it, and throw
it into the basin, you see how it shows the presence of water by lighting up
and floating about, burning with a violet flame. I am now going to take away
the candle which has been burning beneath the vessel containing ice and salt,
and you see a drop of water – a condensed product of the candle – hanging from
the under surface of the dish. I will show you that potassium has the same
action upon it as upon the water in that basin in the experiment we have just
tried. See! it takes fire, and burns in just the same manner. I will take
another drop upon this glass slab, and when I put the potassium on to it, you
see at once, from its taking fire, that there is water present. Now that water
was produced by the candle. In the same manner, if I put this spirit lamp
under that jar, you will soon see the latter become damp from the dew which is
deposited upon it – that dew being the result of combustion; and I have no
doubt you will shortly see, by the drops of water which fall upon the paper
below, that there is a good deal of water produced from the combustion of the
lamp. I will let it remain, and you can afterward see how much water has been
collected. So, if I take a gas lamp, and put any cooling arrangement over it,
I shall get water – water being likewise produced from the combustion of gas.
Here, in this bottle, is a quantity of water – perfectly pure, distilled
water, produced from the combustion of a gas lamp – in no point different from
the water that you distill from the river, or ocean, or spring, but exactly
the same thing. Water is one individual thing; it never changes. We can add to
it by careful adjustment for a little while, or we can take it apart and get
other things from it; but water, as water, remains always the same, either in
a solid, liquid, or fluid state. Here again [holding another bottle] is some
water produced by the combustion of an oil lamp. A pint of oil, when burnt
fairly and properly, produces rather more than a pint of water. Here, again,
is some water, produced by a rather long experiment, from a wax candle. And so
we can go on with almost all combustible substances, and find that if they
burn with a flame, as a candle, they produce water. You may make these
experiments yourselves: the head of a poker is a very good thing to try with,
and if it remains cold long enough over the candle, you may get water
condensed in drops on it; or a spoon, or ladle, or any thing else may be used,
provided it be clean, and can carry off the heat, and so condense the

And now – to go into the history of this wonderful production of water from
combustibles, and by combustion – I must first of all tell you that this water
may exist in different conditions; and although you may now be acquainted with
all its forms, they still require us to give a little attention to them for
the present; so that we may perceive how the water, while it goes through its
Protean changes, is entirely and absolutely the same thing, whether it is
produced from a candle, by combustion, or from the rivers or ocean.

First of all, water, when at the coldest, is ice. Now we philosophers – I
hope that I may class you and myself together in this case – speak of water as
water, whether it be in its solid, or liquid, or gaseous state – we speak of
it chemically as water. Water is a thing compounded of two substances, one of
which we have derived from the candle, and the other we shall find elsewhere.
Water may occur as ice; and you have had most excellent opportunities lately
of seeing this. Ice changes back into water – for we had on our last Sabbath a
strong instance of this change by the sad catastrophe which occurred in our
own house, as well as in the houses of many of our friends – ice changes back
into water when the temperature is raised; water also changes into steam when
it is warmed enough. The water which we have here before us is in its densest
state 11; and, although it changes in weight, in condition, in
form, and in many other qualities, it still is water; and whether we alter it
into ice by cooling, or whether we change it into steam by heat, it increases
in volume in the one case very strangely and powerfully, and in the other case
very largely and wonderfully. For instance, I will now take this tin cylinder,
and pour a little water into it, and, seeing how much water I pour in, you may
easily estimate for yourselves how high it will rise in the vessel: it will
cover the bottom about two inches. I am now about to convert the water into
steam for the purpose of showing to you the different volumes which water
occupies in its different states of water and steam.

[Footnote 11: Water is in its densest state at a temperature of 39.1

Let us now take the case of water changing into ice: we can effect that by
cooling it in a mixture of salt and pounded ice 12 – and I shall do
so to show you to the expansion of water into a thing of larger bulk when it
is so changed. These bottles [holding one] are made strong cast iron, very
strong and very thick – I suppose they are the third of an inch in thickness;
they are very carefully filled with water, so as to exclude all air, and then
they are screwed down tight. We shall see that when we freeze the water in
these iron vessels, they will not be able to hold the ice, and the expansion
within them will break them in pieces as these [pointing to some fragments]
are broken, which have been bottles of exactly the same kind. I am about to
put these two bottles into that mixture of ice and salt for the purpose of
showing that when water becomes ice it changes in volume in this extraordinary

[Footnote 12: A mixture of salt and pounded ice reduces the temperature
from 32 Fahrenheit to zero, the ice at the same time becoming

In the mean time, look at the change which has taken place in the water to
which we have applied heat; it is losing its fluid state. You may tell this by
two or three circumstances. I have covered the mouth of this glass flask, in
which water is boiling, with a watch-glass. Do you see what happens? It
rattles away like a valve chattering, because the steam rising from the
boiling water sends the valve up and down, and forces itself out, and so makes
it clatter. You can very easily perceive that the flask is quite full of
steam, or else it would not force its way out. You see, also, that the flask
contains a substance very much larger than the water, for it fills the whole
of the flask over and over again, and there it is blowing away into the air;
and yet you can not observe any great diminution in the bulk of the water,
which shows you that its change of bulk is very great when it becomes

I have put our iron bottles containing water into this freezing mixture,
that you may see what happens. No communication will take place, you observe,
between the water in the bottles and the ice in the outer vessel. But there
will be a conveyance of heat from the one to the other, and if we are
successful – we are making our experiment in very great haste – I expect you
will by-and-by, so soon as the cold has taken possession of the bottles and
their contents, hear a pop on the occasion of the bursting of the one bottle
or the other, and, when we come to examine the bottles, we shall find their
contents masses of ice, partly inclosed by the covering of iron which is too
small for them, because the ice is larger in bulk than the water. You know
very well that ice floats upon water; if a boy falls through a hole into the
water, he tries to get on the ice again to float him up. Why does the ice
float? Think of that, and philosophize. Because the ice is larger than the
quantity of water which can produce it, and therefore the ice weighs the
lighter and the water is the heavier.

To return now to the action of heat on water. See what a stream of vapor is
issuing from this tin vessel! You observe, we must have made it quite full of
steam to have it sent out in that great quantity. And now, as we can convert
the water into steam by heat, we convert it back into liqui! water by the
application of cold. And if we take a glass, or any other cold thing, and hold
it over this steam, see how soon it gets damp with water: it will condense it
until the glass is warm – it condenses the water which is now running down the
sides of it. I have here another experiment to show the condensation of water
from a vaporous state back into a liquid state, in the same way as the vapor,
one of the products of the candle, was condensed against the bottom of the
dish and obtained in the form of water; and to show you how truly and
thoroughly these changes take place, I will take this tin flask, which is now
full of steam, and close the top. We shall see what takes place when we cause
this water or steam to return back to the fluid state by pouring some cold
water on the outside. [The lecturer poured the cold water over the vessel,
when it immediately collapsed.] You see what has happened. If I had closed the
stopper, and still kept the heat applied to it, it would have burst the
vessel; yet, when the steam returns to the state of water, the vessel
collapses, there being a vacuum produced inside by the condensation of the
steam. I show you these experiments for the purpose of pointing out that in
all these occurrences there is nothing that changes the water into any other
thing; it still remains water; and so the vessel is obliged to give way, and
is crushed inward, as in the other case, by the farther application of heat,
it would have been blown outward.

And what do you think the bulk of that water is when it assumes the
vaporous condition? You see that cube [pointing to a cubic foot]. There, by
its side, is a cubic inch, exactly the same shape as the cubic foot, and that
bulk of water [the cubic inch] is sufficient to expand into that bulk [the
cubic foot] of steam; and, on the contrary, the application of cold will
contract that large quantity of steam into this small quantity of water. [One
of the iron bottles burst at that moment.] Ah! There is one of our bottles
burst, and here, you see, is a crack down one side an eighth of an inch in
width. [The other now exploded, sending the freezing mixture in all
directions.] This other bottle is also broken; although the iron was nearly
half an inch thick, the ice has burst it asunder. These changes always take
place in water; they do not require to be always produced by artificial means;
we only use them here because we want to produce a small winter round that
little bottle instead of a long and severe one. But if you go to Canada, or to
the North, you will find the temperature there out of doors will do the same
thing as has been done here by the freezing mixture.

To return to our quiet philosophy. We shall not in future be deceived,
therefore, by any changes that are produced in water. Water is the same every
where, whether produced from the ocean or from the flame of the candle. Where,
then, is this water which we get from a candle? I must anticipate a little,
and tell you. It evidently comes, as to part of it, from the candle, but is it
within the candle beforehand? No, it is not in the candle; and it is not in
the air around about the candle which is necessary for its combustion. It is
neither in one nor the other, but it comes from their conjoint action, a part
from the candle, a part from the air; and this we have now to trace, so that
we may understand thoroughly what is the chemical history of a candle when we
have it burning on our table. How shall we get at this? I myself know plenty
of ways, but I want you to get at it from the association in your own minds of
what I have already told you.

I think you can see a little in this way. We had just now the case of a
substance which acted upon the water in the way that Sir Humphry Davy showed
us 13, and which I am now going to recall to your minds by making
again an experiment upon that dish. It is a thing which we have to handle very
carefully; for you see, if I allow a little splash of water to come upon this
mass, it sets fire to part of it; and if there were free access of air, it
would quickly set fire to the whole. Now this is a metal – a beautiful and
bright metal – which rapidly changes in the air, and, as you know, rapidly
changes in water. I will put a piece on the water, and you see it burns
beautifully, making a floating lamp, using the water in the place of air.
Again, if we take a few iron filings or turnings and put them in water, we
find that they likewise undergo an alteration. They do not change so much as
this potassium does, but they change somewhat in the same way; they become
rusty, and show an action upon the water, though in a different degree of
intensity to what this beautiful metal does; but they act upon the water in
the same manner generally as this potassium. I want you to put these different
facts together in your minds. I have another metal here [zinc], and when we
examined it with regard to the solid substance produced by its combustion, we
had an opportunity of seeing that it burned; and I suppose, if I take a little
strip of this zinc and put it over the candle, you will see something half
way, as it were, between the combustion of potassium on the water and the
action of iron – you see there is a sort of combustion. It has burned, leaving
a white ash or residuum; and here also we find that the metal has a certain
amount of action upon water.

[Footnote 13: Potassium, the metallic basis of potash, was discovered by
Sir Humphry Davy in 1807, who succeeded in separating it from potash by
means of a powerful voltaic battery. Its great affinity for oxygen causes it
to decompose water with evolution of hydrogen, which takes fire with the
heat produced.]

By degrees we have learned how to modify the action of these different
substances, and to make them tell us what we want to know. And now, first of
all, I take iron. It is a common thing in all chemical reactions, where we get
any result of this kind, to find that it is increased by the action of heat;
and if we want to examine minutely and carefully the action of bodies one upon
another, we often have to refer to the action of heat. You are aware, I
believe, that iron filings burn beautifully in the air; but I am about to show
you an experiment of this kind, because it will impress upon you what I am
going to say about iron in its action on water. If I take a flame and make it
hollow – you know why, because I want to get air to it and into it, and
therefore I make it hollow – and then take a few iron filings and drop them
into the flame, you see how well they burn. That combustion results from the
chemical action which is going on when we ignite those particles. And so we
proceed to consider these different effects, and ascertain what iron will do
when it meets with water. It will tell us the story so beautifully, so
gradually and regularly, that I think it will please you very much.

I have here a furnace with a pipe going through it like an iron gun barrel,
and I have stuffed that barrel full of bright iron turnings, and placed it
across the fire to be made red-hot. We can either send air through the barrel
to come in contact with the iron, or we can send steam from this little boiler
at the end of the barrel. Here is a stop-cock which shuts off the steam from
the barrel until we wish to admit it. There is some water in these glass jars,
which I have colored blue, so that you may see what happens. Now you know very
well that any steam I might send through that barrel, if it went through into
the water, would be condensed; for you have seen that steam can not retain its
gaseous form if it be cooled down; you saw it here [pointing to the tin flask]
crushing itself into a small bulk, and causing the flask holding it to
collapse; so that if I were to send steam through that barrel it would be
condensed, supposing the barrel were cold; it is, therefore, heated to perform
the experiment I am now about to show you. I am going to send the steam
through the barrel in small quantities, and you shall judge for yourselves,
when you see it issue from the other end, whether it still remains steam.
Steam is condensible into water, and when you lower the temperature of steam
you convert it back into fluid water; but I have lowered the temperature of
the gas which I have collected in this jar by passing it through water after
it has traversed the iron barrel, and still it does not change back into
water. I will take another test and apply to this gas. (I hold the jar in an
inverted position, or my substance would escape.) If I now apply a light to
the mouth of the jar, it ignites with a slight noise. That tells you that it
is not steam; steam puts out a fire; it does not burn; but you saw that what I
had in that jar burnt. We may obtain this substance equally from water
produced from the candle flame as from any other source. When it is obtained
by the action of the iron upon the aqueous vapor, it leaves the iron in a
state very similar to that in which these filings were after they were burnt.
It makes the iron heavier than it was before. So long as the iron remains in
the tube and is heated, and is cooled again without the access of air or
water, it does not change in its weight; but after having had this current of
steam passed over it, it then comes out heavier than it was before, having
taken something out of the steam, and having allowed something else to pass
forth, which we see here. And now, as we have another jar full, I will show
you something most interesting. It is a combustible gas; and I might at once
take this jar and set fire to the contents, and show you that it is
combustible; but I intend to show you more, if I can. It is also a very light
substance. Steam will condense; this body will rise in the air, and not
condense. Suppose I take another glass jar, empty of all but air: if I examine
it with a taper I shall find that it contains nothing but air. I will now take
this jar full of the gas that I am speaking of, and deal with it as though it
were a light body; I will hold both upside down, and turn the one up under the
other; and that which did contain the gas procured from the steam, what does
it contain now? You will find it now only contains air. But look! Here is the
combustible substance [taking the other jar] which I have poured out of the
one jar into the other. It still preserves its quality, and condition, and
independence, and therefore is the more worthy of our consideration, as
belonging to the products of a candle.

Now this substance which we have just prepared by the action of iron on the
steam or water, we can also get by means of those other things which you have
already seen act so well upon the water. If I take a piece of potassium, and
make the necessary arrangements, it will produce this gas; and if, instead, a
piece of zinc, I find, when I come to examine it very carefully, that the main
reason why this zinc can not act upon the water continuously as the other
metal does, is because the result of the action of the water envelops the zinc
in a kind of protecting coat. We have learned in consequence, that if we put
into our vessel only the zinc and water, they, by themselves, do not give rise
to much action, and we get no result. But suppose I proceed to dissolve off
this varnish – this encumbering substance – which I can do by a little acid;
the moment I do this I find the zinc acting upon the water exactly as the iron
did, but at the common temperature. The acid in no way is altered, except in
its combination with the oxide of zinc which is produced. I have now poured
the acid into the glass, and the effect is as though I were applying heat to
cause this boiling up. There is something coming off from the zinc very
abundantly, which is not steam. There is a jar full of it; and you will find
that I have exactly the same combustible substance remaining in the vessel,
when I hold it upside down, that I produced during the experiment with the
iron barrel. This is what we get from water, the same substance which is
contained in the candle.

Let us now trace distinctly the connection between these two points. This
is hydrogen – a body classed among those things which in chemistry we call
elements, because we can get nothing else out of them. A candle is not an
elementary body, because we can get carbon out of it; we can bet this hydrogen
out of it, or at least out of the water which it supplies. And this gas has
been so named hydrogen, because it is that element which, in association with
another generates water. 14 Mr. Anderson having now been able to
get two or three jars of gas, we shall have a few experiments to make, and I
want to show you the best way of making these experiments. I am not afraid to
show you, for I wish you to make experiments, if you will only make them with
care and attention, and the assent of those around you. As we advance in
chemistry we are obliged to deal with substances which are rather injurious if
in their wrong places; the acids, and heat, and conbustible things we use,
might do harm if carelessly employed. If you want to make hydrogen, you can
make it easily from bits of zinc, and sulphuric or pipe into the suds and blow
bubbles by means of the hydrogen. You observe how the bubbles fall downward
when I blow them with my warm breath; but notice the difference when I blow
them with hydrogen. [The lecturer here blew bubbles with hydrogen, which rose
to the roof of the theatre.] It shows you how light this gas must be in order
to carry with it not merely the ordinary soap bubble, but the larger portion
of a drop hanging to the bottom of it. I can show its lightness in a better
way than this; larger bubbles than these may be so lifted up; indeed, in
former times balloons used to be filled with this gas. Mr. Anderson will
fasten this tube on to our generator, and we shall have a stream of hydrogen
here with which we can charge this balloon made of collodion. I need not even
be very careful to get all air out, for I know the power of this gas to carry
it up. [Two collodion balloons were inflated and sent up, one being held by a
string.] Here is another larger one, made of thin membrane, which we will fill
and allow to ascend; you will see they will all remain floating about until
the gas escapes.

[Footnote 14: Yowp, “water,” and yevvaw, “I generate.”]

What, then, are the comparative weights of these substances? I have a table
here which will show you the proportion which their weights bear to each
other. I have taken a pint and a cubic foot as the measures, and have placed
opposite to them the respective figures. A pint measure of this hydrogen
weighs three-quarters of our smallest weight, a grain, and a cubic foot weighs
one-twelfth of an ounce; whereas a pint of water weighs 8,750 grains, and a
cubic foot of water weighs almost 1,000 ounces. You see, therefore, what a
vast difference there is between the weight of a cubic foot of water and a
cubic foot of hydrogen.

Hydrogen gives rise to no substance that can become solid, either during
combustion or afterward as a product of its combustion; but when it burns it
produces water only; and if we take a cold glass and put it over the flame, it
becomes damp, and you have water produced immediately in appreciable quantity;
and nothing is produced by its combustion but the same water which you have
seen the flame of the candle produce. It is important to remember that this
hydrogen is the only thing in nature which furnishes water as the sole product
of combustion.

And now we must endeavor to find some additional proof of the general
character and composition of water, and for this purpose I will keep you a
little longer, so that at our next meeting we may be better prepared for the
subject. We have the power of arranging the zinc which you have seen acting
upon the water by the assistance of an acid, in such a manner as to cause all
the power to be evolved in the place where we require it. I have behind me a
voltaic pile, and I am just about to show you, at the end of this lecture, its
character and power, that you may see what we shall have to deal with when
next we meet. I hold here the extremities of the wires which transport the
power from behind me, and which I shall cause to act on the water.

We have previously seen what a power of combustion is possessed by the
potassium, or the zinc, or the iron filings; but none of them show such energy
as this. [The lecturer here made contact between the two terminal wires of the
battery, when a brilliant flash of light was produced.] This light is, in
fact, produced by a forty-zinc power of burning; it is a power that I can
carry about in my hands through these wires at pleasure, although if I applied
it wrongly to myself, it would destroy me in an instant, for it is a most
intense thing, and the power you see here put forth while you count five
[bringing the poles in contact and exhibiting the electric light] is
equivalent to the power of several thunder-storms, so great is its force
15. And that you may see what intense energy it has, I will take
the ends of the wires which convey the power from the battery, and with it I
dare say I can burn this iron file. Now this is a chemical power, and one
which, when we next meet, I shall apply to water, and show you what results we
are able to produce.

[Footnote 15: Professor Faraday has calculated that there is as much
electricity required to decompose one grain of water as there is in a very
powerful flash of lightning.]


Lecture IV: Hydrogen In The
Candle – Burns Into Water – The Other Part Of Water –

I see you are not tired of the candle yet, or I am sure you would not be
interested in the subject in the way you are. When our candle was burning we
found it produced water exactly like the water we have around us; and by
farther examination of this water we found in it that curious body, hydrogen
that light substance of which there is some in this jar. We afterward saw the
burning powers of that hydrogen, and that it produced water. And I think I
introduced to your notice an apparatus which I very briefly said was an
arrangement of chemical force, or power, or energy, so adjusted as to convey
its power to us in these wires; and I said I should use that force to pull the
water to pieces, to see what else there was in the water besides hydrogen;
because, you remember, when we passed the water through the iron tube, we by
no means got the weight of water back which we put in in the form of steam,
though we had a very large quantity of gas evolved. We have now to see what is
the other substance present. That you may understand the character and use of
this instrument, let us make an experiment or two. Let us put together, first
of all, some substances, knowing what they are, and then see what that
instrument does to them. There is some copper (observe the various changes
which it can undergo), and here is some nitric acid, and you will find that
this, being a strong chemical agent, will act very powerfully when I add it to
the copper. It is now sending forth a beautiful red vapor; but as we do not
want that vapor, Mr. Anderson will hold it near the chimney for a short time,
that we may have the use and beauty of the experiment without the annoyance.
The copper which I have put into the flask will dissolve it: it will change
the acid and the water into a blue fluid containing copper and other things,
and I purpose then showing you how this voltaic battery deals with it; and in
the mean time we will arrange another kind of experiment for you to see what
power it has. This is a substance which is to us like water – that is to say,
it contains bodies which we do not know of as yet, as water contains a body
which we do not know as yet. Now this solution of a salt 16 I will
put upon paper, and spread about, and apply the power of the battery to it,
and observe what will happen. Three or four important things will happen which
we shall take advantage of. I place this wetted paper upon a sheet of tin
foil, which is convenient for keeping all clean, and also for the advantageous
application of the power; and this solution, you see, is not at all affected
by being put upon the paper or tin foil, nor by any thing else I have brought
in contact with it yet, and which, therefore, is free to us to use as regards
that instrument. But first let us see that our instrument is in order. Here
are our wires. Let us see whether it is in the state in which it was last
time. We can soon tell. As yet, when I bring them together, we have no power,
because the conveyers – what we call the electrodes – the passages or ways for
the electricity – are stopped; but now Mr. Anderson by that [referring to a
sudden flash at the ends of the wires] has given me a telegram to say that it
is ready. Before I begin our experiment I will get Mr. Anderson to break
contact again at the battery behind me, and we will put a platinum wire across
to connect the poles, and then if I find I can ignite a pretty good length of
this wire we shall be safe in our experiment. Now you will see the power. [The
connection was established, and the intermediate wire became red-hot.] There
is the power running beautifully through the wire, which I have made thin on
purpose to show you that we have those powerful forces; and now, having that
power, we will proceed with it to the examination of water.


[Footnote 16: A solution of acetate of lead submitted to the action of
the voltaic current yields lead at the negative pole, and brown peroxide of
lead at the positive pole. A solution of nitrate of silver, under the same
circumstances, yields silver at the negative pole, and peroxide of silver at
the positive pole.]

I have here two pieces of platinum, and if I lay them down upon this piece
of paper [the moistened paper on the tin foil] you will see no action; and if
I take them up there is no change that you can see, but the arrangement
remains just as it was before. But, now, see what happens: if I take these two
poles and put either one or the other of them down separately on the platinum
plates, they do nothing for me; both are perfectly without action; but if I
let them both be in contact at the same moment, see what happens [a brown spot
appeared under each pole of the battery]. Look here at the effect that takes
place, and see how I have pulled something apart from the white something
brown; and I have no doubt, if I were to arrange it thus, and were to put one
of the poles to the tin foil on the other side of the paper – why, I get such
a beautiful action upon the paper that I am going to see whether I can not
write with it – a telegram, if you please. [The lecturer here traced the word
“juvenile” on the paper with one of the terminal wires.] See there how
beautifully we can get our results!

You see we have here drawn something which we have not known about before
out of this solution. Let us now take that flask from Mr. Anderson’s hands,
and see what we can draw out of that. This, you know, is a liquid which we
have just made up from copper and nitric acid while our other experiments were
in hand; and though I am making this experiment very hastily, and may bungle a
little, yet I prefer to let you see what I do rather than prepare it

Now see what happens. These two platinum plates are the two ends (or I will
make them so immediately) of this apparatus; and I am about to put them in
contact with that solution, just as we did a moment ago on the paper. It does
not matter to us whether the solution be on the paper or whether it be in the
jar, so long as we bring the ends of the apparatus to it. If I put the two
platinums in by themselves they come out as clean and as white as they go in
[inserting them into the fluid without connecting them with the battery]; but
when we take the power and lay that on [the platinums were connected with the
battery and again dipped into the solution], this, you see [exhibiting one of
the platinums], is at once turned into copper, as it were; it has become like
a plate of copper; and that [exhibiting the other piece of platinum] has come
out quite clean. If I take this coppered piece and change sides, the copper
will leave the right-hand side and come over to the left side; what was before
the coppered plate comes out clean, and the plate which was clean comes out
coated with copper; and thus you see that the same copper we put into this
solution we can also take out of it by means of this instrument.

Putting that solution aside, let us now see what effect this instrument
will have upon water. Here are two little platinum plates which I intend to
make the ends of the battery, and this (C) is a little vessel so shaped as to
enable me to take it to pieces, and show you its construction. In these two
cups (A and B) I pour mercury, which touches the ends of the wires connected
with the platinum plates. In the vessel (C) I pour some water containing a
little acid (but which is put in only for the purpose of facilitating the
action; it undergoes no change in the process), and connected with the top of
the vessel is a bent glass tube (D), which may remind you of the pipe which
was connected with the gun barrel in our furnace experiment, and which now
passes under the jar (F). I have now adjusted this apparatus, and we will
proceed to affect the water in some way or other. In the other case I sent the
water through a tube which was made red-hot; I am now going to pass the
electricity through the contents of this vessel. Perhaps I may boil the water;
if I do boil the water, I shall get vessel, which is now quite clear and
bright, will become dim. There will be no sound, for the vessel is strong
enough to confine the explosion. [A spark was then passed through the jar,
when the explosive mixture was ignited.] Did you see that brilliant light? If
I again screw the vessel on to the jar, and open these stop-cocks, you will
see that the gas will rise a second time. [The stop-cocks were then opened.]
Those gases [referring to the gases first collected in the jar, and which had
just been ignited by the electric spark] have disappeared, as you see; their
place is vacant, and fresh gas has gone in. Water has been formed from them;
and if we repeat our operation [repeating the last experiment], I shall have
another vacancy, as you will see by the water rising. I always have an empty
vessel after the explosion, because the vapor or gas into which that water has
been resolved by the battery explodes under the influence of the spark, and
changes into water; and by-and-by you will see in this upper vessel some drops
of water trickling down the sides and collecting at the bottom.

We are here dealing with water entirely, without reference to the
atmosphere. The water of the candle had the atmosphere helping to produce it;
but in this way it can be produced independently of the air. Water, therefore,
ought to contain that other substance which the candle takes from the air, and
which, combining with the hydrogen, produces water.

Just now you saw that one end of this battery took hold of the copper,
extracting it from the vessel which contained the blue solution. It was
effected by this wire; and surely we may say, if the battery has such power
with a metallic solution which we made and unmade, may we not find that it is
possible to split asunder the component parts of the water, and put them into
this place and that place? Suppose I take the poles – the metallic ends of
this battery – and see what will happen with the water in this apparatus,
where we have separated the two ends far apart. I place one here (at A), and
the other there (at B); and I have little shelves with holes which I can put
upon each pole, and so arrange them that whatever escapes from the two ends of
the battery will appear as separate gases; for you saw that the water did not
become vaporous, but gaseous. The wires are now in perfect and proper
connection with the vessel containing the water, and you see the bubbles
rising; let us collect these bubbles and see what they are. Here is a glass
cylinder (O); I fill it with water and put it over one end (A) of the pile,
and I will take another (H), and put it over the other end (B) of the pile.
And so now we have a double apparatus, with both places delivering gas. Both
these jars will fill with gas. There they go, that to the right (H) filling
very rapidly; the one to the left (O) filling not so rapidly; and, though I
have allowed some bubbles to escape, yet still the action is going on pretty
regularly; and were it not that one is rather smaller than the other, you
would see that I should have twice as much in this (H) as I have in that (O).
Both these gases are colorless; they stand over the water without condensing;
they are alike in all things – I mean in all apparent things; and we have here
an opportunity of examining these bodies and ascertaining what they are. Their
bulk is large, and we can easily apply experiments to them. I will take this
jar (H) first, and will ask you to be prepared to recognize hydrogen.

Think of all its qualities – the light gas which stood well in inverted
vessels, burning with a pale flame at the mouth of the jar, and see whether
this gas does not satisfy all these conditions. If it be hydrogen it will
remain here while I hold this jar inverted. [A light was then applied, when
the hydrogen burnt.] What is there now in the other jar? You know that the two
together made an explosive mixture. But what can this be which we find as the
other constituent in water, and which must therefore be that substance which
made the hydrogen burn? We know that the water we put into the vessel
consisted of the two things together. We find one of these is hydrogen: what
must that other be which was in the water before the experiment, and which we
now have by itself? I am about to put this lighted splinter of wood into the
gas. The gas itself will not burn, but it will make the splinter of wood burn.
[The lecturer ignited the end of the wood and introduced it into the jar of
gas.] See how it invigorates the combustion of the wood, and how it makes it
burn far better than the air would make it burn; and now you see by itself
that every other substance which is contained in the water, and which, when
the water was formed by the burning of the candle, must have been taken from
the atmosphere. What shall we call it, A, B, or C? Let us call it O – call it
“Oxygen”; it is a very good, distinct – sounding name. This, then, is the
oxygen which was present in the water, forming so large a part of it.

We shall now begin to understand more clearly our experiments and
researches, because when we have examined these things once or twice we shall
soon see why a candle burns in the air. When we have in this way analyzed the
water – that is to say, separated or electrolyzed its parts out of it, we get
two volumes of hydrogen and one of the body that burns it. And these two are
represented to us on the following diagram, with their weights also stated;
and we shall find that the oxygen is a very heavy body by comparison with the
hydrogen. It is the other element in water.

[Table 1]

I had better, perhaps, tell you now how we get this oxygen abundantly,
having shown you how we can separate it from the water. Oxygen, as you will
immediately imagine, exists in the atmosphere; for how should the candle burn
to produce water without it? Such a thing would be absolutely impossible, and
chemically impossible, without oxygen. Can we get it from the air? Well, there
are some very complicated and difficult processes by which we can get it from
the air; but we have better processes. There is a substance called the black
oxide of manganese; it is a very black-looking mineral, but very useful, and
when made red-hot it gives out oxygen. Here is an iron bottle which has had
some of this substance put into it, and there is a tube fixed to it, and a
fire ready made, and Mr. Anderson will put that retort into the fire, for it
is made of iron, and can stand the heat. Here is a salt called chlorate of
potassa, which is now made in large quantities for bleaching, and chemical and
medical uses, and for pyrotechnic and other purposes. I will take some and mix
it with some of the oxide of manganese (oxide of copper, or oxide of iron
would do as well); and if I put these together in a retort, far less than a
red heat is sufficient to evolve this oxygen from the mixture. I am not
preparing to make much, because we only want sufficient for our experiments;
only, as you will see immediately, if I use too small a charge, the first
portion of the gas will be mixed with the air already in the retort, and I
should be obliged to sacrifice the first portion of the gas because it would
be so much diluted with air; the first portion must therefore be thrown away.
You will find in this case that a common spirit lamp is quite sufficient for
me to get the oxygen, and so we shall have two processes going on for its
preparation. See how freely the gas is coming over from that small portion of
the mixture. We will examine it and see what are its properties. Now in this
way we are producing, as you will observe, a gas just like the one we had in
the experiment with the battery, transparent, undissolved by water, and
presenting the ordinary visible properties of the atmosphere. (As this first
jar contains the air, together with the first portions of the oxygen set free
during the preparation, we will carry it out of the way, and be prepared to
make our experiments in a regular, dignified manner.) And inasmuch as that
power of making wood, wax, or other things burn, was so marked in the oxygen
we obtained by means of the voltaic battery from water, we may expect to find
the same property here. We will try it. You see there is the combustion of a
lighted taper in air, and here is its combustion in this gas [lowering the
taper into the jar]. See how brightly and how beautifully it burns! You can
also see more than this: you will perceive it is a heavy gas, while the
hydrogen would go up like a balloon, or even faster than a balloon, when not
encumbered with the weight of the envelope. You may easily see that although
we obtained from water twice as much in volume of the hydrogen as of oxygen,
it does not follow that we have twice as much in weight, because one is heavy
and the other a very light gas. We have means of weighing gases or air; but,
without stopping to explain that, let me just tell you what their respective
weights are. The weight of a pint of hydrogen is three-quarters of a grain;
the weight of the same quantity of oxygen is nearly twelve grains. This is a
very great difference. The weight of a cubic foot of hydrogen is one-twelfth
of an ounce; and the weight of a cubic foot of oxygen is one ounce and a
third. And so on we might come to masses of matter which may be weighed in the
balance, and which we can take account of as to hundred-weights and as to
tons, as you will see almost immediately.

Now, as regards this very property of oxygen supporting combustion, which
we may compare to air, I will take a piece of candle to show it you in a rough
way – and the result will be rough. There is our candle burning in the air:
how will it burn in oxygen? I have here a jar of this gas, and I am about to
put it over the candle for you to compare the action of this gas with that of
the air. Why, look at it; it looks something like the light you saw at the
poles of the voltaic battery. Think how vigorous that action must be. And yet,
during all that action, nothing more is produced than what is produced by the
burning of the candle in air. We have the same production of water, and the
same phenomena exactly, when we use this gas instead of air, as we have when
the candle is burnt in air.

But now we have got a knowledge of this new substance, we can look at it a
little more distinctly, in order to satisfy ourselves that we have got a good
general understanding of this part of the product of a candle. It is wonderful
how great the supporting powers of this substance are as regards combustion.
For instance, here is a lamp which, simple though it be, is the original, I
may say, of a great variety of lamps which are constructed for divers purposes
– for lighthouses, microscopic illuminations, and other uses; and if it was
proposed to make it burn very brightly, you would say, “If a candle burnt
better in oxygen, will not a lamp do the same?” Why, it will do so. Mr.
Anderson will give me a tube coming from our oxygen reservoir, and I am about
to apply it to this flame, which I will previously make burn badly on purpose.
There comes the oxygen: what a combustion that makes! But if I shut it off,
what becomes of the lamp? [The flow of oxygen was stopped, and the lamp
relapsed to its former dimness.] It is wonderful how, by means of oxygen, we
get combustion accelerated. But it does not affect merely the combustion of
hydrogen, or carbon, or the candle, but it exalts all combustions of the
common kind. We will take one which relates to iron, for instance, as you have
already seen iron burn a little in the atmosphere. Here is a jar of oxygen,
and this is a piece or iron wire; but if it were a bar as thick as my wrist,
it would burn the same. I first attach a little piece of wood to the iron; I
then set the wood on fire, and let them both down together into the jar. The
wood is now alight, and there it burns as wood should burn in oxygen; but it
will soon communicate its combustion to the iron. The iron is now burning
brilliantly, and will continue so for a long time. As long as we supply
oxygen, so long we can carry on the combustion of the iron, until the latter
is consumed.

We will now put that on one side, and take some other substance; but we
must limit our experiments, for we have not time to spare for all the
illustrations you would have a right to if we had more time. We will take a
piece of sulphur: you know how sulphur burns in the air; well, we put it into
the oxygen, and you will see that whatever can burn in air can burn with a far
greater intensity in oxygen, leading you to think that perhaps the atmosphere
itself owes all its power of combustion to this gas. The sulphur is now
burning very quietly in the oxygen; but you can not for a moment mistake the
very high and increased action which takes place when it is so burnt, instead
of being burnt merely in common air.

I am now about to show you the combustion of another substance phosphorus.
I can do it better for you here than you can do it at home. This is a very
combustible substance; and if it be so combustible in air, what might you
expect it would be in oxygen? I am about to show it to you not in its fullest
intensity, for if I did so we should almost blow the apparatus up; I may even
now crack the jar, though I do not want to break things carelessly. You see
how it burns in the air. But what a glorious light it gives out when I
introduce it into oxygen! [Introducing the lighted phosphorus into the jar of
oxygen.] There you see the solid particles going off which cause the
combustion to be so brilliantly luminous.

Thus far we have tested this power of oxygen, and the high combustion it
produces, by means of other substances. We must now, for a little while
longer, look at it as respects the hydrogen. You know, when we allowed the
oxygen and the hydrogen derived from the water to mix and burn together, we
had a little explosion. You remember also that when I burnt the oxygen and the
hydrogen in a jet together, we got very little light, but great heat; I am now
about to set fire to oxygen and hydrogen mixed in the proportion in which they
occur in water. Here is a vessel containing one volume of oxygen and two
volumes of hydrogen. This mixture is exactly of the same nature as the gas we
just now obtained from the voltaic battery; it would be far too much to burn
at once; I have therefore arranged to blow soap bubbles with it and burn those
bubbles, that we may see by a general experiment or two how this oxygen
supports the combustion of the hydrogen. First of all, we will see whether we
can blow a bubble. Well, there goes the gas [causing it to issue through a
tobacco-pipe into some soapsuds]. Here I have a bubble. I am receiving them on
my hand, and you will perhaps think I am acting oddly in this experiment, but
it is to show you that we must not always trust to noise and sounds, but
rather to real facts. [Exploding a bubble on the palm of his hand.] I am
afraid to fire a bubble from the end of the pipe, because the explosion would
pass up into the jar and blow it to pieces. This oxygen then, will unite with
the hydrogen, as you see by the phenomena, and hear by the sound, with the
utmost readiness of action, and all its powers to then taken up in its
neutralization of the qualities of the hydrogen.

So now I think you will perceive the whole history of water with reference
to oxygen and the air from what we have before said. Why does a piece of
potassium decompose water? Because it finds oxygen in the water. What is set
free when I put it in the water, as I am about to do again? It sets free
hydrogen, and the hydrogen burns; but the potassium itself combines with
oxygen; and this piece of potassium, in taking the water apart – the water,
you may say, derived from the combustion of the candle – takes away the oxygen
which the candle took from the air, and so sets the hydrogen free; and even if
I take a piece of ice, and put a piece of potassium upon it, the beautiful
affinities by which the oxygen and the hydrogen are related are such that the
ice will absolutely set fire to the potassium. I show this to you to-day, in
order to enlarge your ideas of these things, and that you may see how greatly
results are modified by circumstances. There is the potassium on the ice,
producing a sort of volcanic action.

It will be my place when next we meet, having pointed out these anomalous
actions, to show you that none of these extra and strange effects are met with
by us – that none of these strange and injurious actions take place when we
are burning, not merely a candle, but gas in our streets, or fuel in our
fireplaces, so long as we confine ourselves within the laws that Nature has
made for our guidance.


Lecture V: Oxygen Present In The
Air – Nature Of The Atmosphere – Carbonic Acid

We have now seen that we can produce hydrogen and oxygen from the water
that we obtained from the candle. Hydrogen, you know, comes from the candle,
and oxygen, you believe, comes from the air. But then you have a right to ask
me, “How is it that the air and the oxygen do not equally well burn the
candle?” If you remember what happened when I put a jar of oxygen over a piece
of candle, you recollect there was a very different kind of combustion to that
which took place in the air. Now, why is this? It is a very important
question, and one I shall endeavor to make you understand; it relates most
intimately to the nature of the atmosphere, and is most important to us.

We have several tests for oxygen besides the mere burning of bodies; you
have seen a candle burnt in oxygen or in the air; you have seen phosphorus
burnt in the air or in oxygen, and you have seen iron filings burnt in oxygen.
But we have other tests besides these, and I am about to refer to one or two
of them for the purpose of carrying your conviction and your experience
farther. Here we have a vessel of oxygen. I will show its presence to you: If
I take a little spark and put it into that oxygen, you know by the experience
you gained the last time we met what will happen – if I put that spark into
the jar, it will tell you whether we have oxygen here or not. Yes! We have
proved it by combustion; and now here is another test for oxygen, which is a
very curious and useful one. I have here two jars full of gas, with a plate
between them to prevent their mixing; I take the plate away, and the gases are
creeping one into the other. “What happens?” say you; “they together produce
no such combustion as was seen in the case of the candle.” But see how the
presence of oxygen is told by its association with this other substance.
17 What a beautifully colored gas I have obtained in this way,
showing me the presence of the oxygen! In the same way we can try this
experiment by mixing common air with this test-gas. Here is a jar containing
air-such air as the candle would burn in – and here is a jar or bottle
containing the test – gas. I let them come together over water, and you see
the result: the contents of the test-bottle are flowing into the jar of air,
and you see I obtain exactly the same kind of action as before, and that shows
me that there is oxygen in the air – the very same substance that has been
already obtained by us from the water produced by the candle. But then, beyond
that, how is it that the candle does not burn in air as well as in oxygen? We
will come to that point at once. I have here two jars; they are filled to the
same height with gas, and the appearance to the eye is alike in both, and I
really do not know at present which of these jars contains oxygen and which
contains air, although I know they have previously been filled with these
gases. But here is our test-gas, and I am going to work with the two jars, in
order to examine whether there is any difference between them in the quality
of reddening this gas. I am now going to turn this test-gas into one of the
jars, and observe what happens. There is reddening, you see; there is, then,
oxygen present. We will now test the other jar; but you see this is not so
distinctly red as the first, and, farther, this curious thing happens; if I
take these two gases and shake them well together with water, we shall absorb
the red gas; and then, if I put in more of this test-gas and shake again, we
shall absorb more; and I can go on as long as there be any oxygen present to
produce that effect. If I let in air, it will not matter; but the moment I
introduce water, the red gas disappears; and I may go on in this way, putting
in more and more of the test – gas, until I come to something left behind
which will not redden any longer by the use of that particular body that
rendered the air and the oxygen red. Why is that? You see in a moment it is
because there is, besides oxygen, something else present which is left behind.
I will let a little more air into the jar, and if it turns red you will know
that some of that reddening gas is still present, and that, consequently, it
was not for the want of this producing body that that air was left behind.

[Footnote 17: The gas which is thus employed as a test for the presence
of oxygen is the binoxide of nitrogen, or nitrous oxide. It is a colorless
gas, which, when brought in contact with oxygen, unites with it, forming
hyponitric acid, the red gas referred to.]

Now you will begin to understand what I am about to say. You saw that when
I burnt phosphorus in a jar, as the smoke produced by the phosphorus and the
oxygen of the air condensed, it left a good deal of gas unburnt, just as this
red gas left something untouched; there was, in fact, this gas left behind,
which the phosphorus can not touch, which the reddening gas can not touch, and
this something is not oxygen, and yet is part of the atmosphere.

So that is one way of opening out air into the two things of which it is
composed – oxygen, which burns our candles, our phosphorus, or any thing else,
and this other substance – nitrogen – which will not burn them. This other
part of the air is by far the larger proportion, and it is a very curious body
when we come to examine it; it is remarkably curious, and yet you say,
perhaps, that it is very uninteresting. It is uninteresting in some respects
because of this, that it shows no brilliant effects of combustion. If I test
it with a taper as I do oxygen and hydrogen, it does not burn like hydrogen,
nor does it make the taper burn like oxygen. Try it in any way I will, it does
neither the one thing nor the other; it will not take fire; it will not let
the taper burn; it puts out the combustion of every thing. There is nothing
that will burn in it in common circumstances. It has no smell; it is not sour;
it does not dissolve in water; it is neither an acid nor an alkali; it is as
indifferent to all our organs as it is possible for a thing to be. And you
might say, “It is nothing; it is not worth chemical attention; what does it do
in the air?” Ah! then come our beautiful and fine results shown us by an
observant philosophy. Suppose, in place of having nitrogen, or nitrogen and
oxygen, we had pure oxygen as our atmosphere; what would become of us? You
know very well that a piece of iron lit in a jar of oxygen goes on burning to
the end. When you see a fire in an iron grate, imagine where the grate would
go to if the whole of the atmosphere were oxygen. The grate would burn up more
powerfully than the coals; for the iron of the grate itself is even more
combustible than the coals which we burn in it. A fire put into the middle of
a locomotive would be a fire in a magazine of fuel, if the atmosphere were
oxygen. The nitrogen lowers it down and makes it moderate and useful for us,
and then, with all that, it takes away with it the fumes that you have seen
produced from the candle, disperses them throughout the whole of the
atmosphere, and carries them away to places where they are wanted to perform a
great and glorious purpose of good to man, for the sustenance of vegetation,
and thus does a most wonderful work, although you say, on examining it, “Why,
it is a perfectly indifferent thing.” This nitrogen in its ordinary state is
an inactive element; no action short of the most intense electric force, and
then in the most infinitely small degree, can cause the nitrogen to combine
directly with the other element of the atmosphere, or with other things round
about it; it is a perfectly indifferent, and therefore to say, a safe

But, before I take you to that result, I must tell you about the atmosphere
itself. I have written on this diagram the composition of one hundred parts of
atmospheric air:

—Table 2]

It is a true analysis of the atmosphere so far as regards the quantity of
oxygen and the quantity of nitrogen present. By our analysis, we find that 5
pints of the atmosphere contain only 1 pint of oxygen, and 4 pints, or 4
parts, of nitrogen by bulk. That is our analysis of the atmosphere. It
requires all that quantity of nitrogen to reduce the oxygen down, so as to be
able to supply the candle properly with fuel, so as to supply us with an
atmosphere which our lungs can healthily and safely breathe; for it is just as
important to make the oxygen right for us to breathe, as it is to make the
atmosphere right for the burning of the fire and the candle.

But now for this atmosphere. First of all, let me tell you the weight of
these gases. A pint of nitrogen weighs 10 4-10 grains, or a cubic foot weighs
1 1-6 ounces. That is the weight of the nitrogen. The oxygen is heavier: a
pint of it weighs 11 9-10 grs., and a cubic foot weighs 1 3-4 oz. A pint of
air weighs about 10 7-10 grs., and a cubic foot 1 1-5 oz.

You have asked me several times, and I am very glad you have, “How do you
weigh gases?” I will show you: it is very simple, and easily done. Here is a
balance, and here a copper bottle, made as light as we can consistent with due
strength, turned very nicely in the lathe, and made perfectly air-tight, with
a stop-cock, which we can open and shut, which at present is open, and,
therefore, allows the bottle to be full of air. I have here a nicely adjusted
balance in which I think the bottle, in its present condition, will be
balanced by the weight on the other side. And here is a pump by which we can
force the air into this bottle, and with it we will force in a certain number
of volumes of air as measured by the pump. [Twenty measures were pumped in.]
We will shut that in and put it in the balance. See how it sinks; it is much
heavier than it was. By what? By the air that we have forced into it by the
pump. There is not a greater bulk of air, but there is the same bulk of
heavier air, because we have forced in air upon it. And that you may have a
fair notion in your mind as to how much this air measures, here is a jar full
of water. We will open that copper vessel into this jar, and let the air
return to its former state. All I have to do now is to screw them tightly
together, and to turn the taps, when there, you see, is the bulk of the twenty
pumps of air which I forced into the bottle; and to make sure that we have
been quite correct in what we have been doing, we will take the bottle again
to the balance, and, if it is now counterpoised by the original weight, we
shall be quite sure we have made our experiment correctly. It is balanced; so,
you see, we can find out the weight of the extra volumes of air forced in that
way, and by that means we are able to ascertain that a cubic foot of air
weighs 1 1-5 oz. But that small experiment will by no means convey to your
mind the whole literal truth of this matter. It is wonderful how it
accumulates when you come to larger volumes. This bulk of air [a cubic foot]
weighs 1 1-5 oz. What do you think of the contents of that box above there
which I have had made for the purpose? The air which is within that box weigh
one pound – a full pound; and I have calculated the weight of the air in this
room: you would hardly imagine it, but it is above a ton. So rapidly do the
weights rise up, and so important is the presence to the atmosphere, and of
the oxygen and the nitrogen in it, and the use it performs in conveying things
to and fro from place to place, and carrying bad vapors to places where they
will do good instead of harm.

Having given you that little illustration with respect to the weight of the
air, let me show you certain consequences of it. You have a right to them,
because you would not understand so much without it. Do you remember this kind
of experiment? Have you ever seen it? Suppose I take a pump somewhat similar
to the one I had a little while ago to force air into the bottle, and suppose
I place it in such a manner that by certain arrangements I can apply my hand
to it. My hand moves about in the air so easily that it seems to feel nothing,
and I can hardly get velocity enough by any motion of my own in the atmosphere
to make sure that there is much resistance to it. But when I put my hand here
[on the air-pump receiver, which was afterward exhausted] you see what
happens. Why is my hand fastened to this place, and why am I able to pull this
pump about? And see! how is it that I can hardly get my hand away? Why is
this? It is the weight of the air – the weight of the air that is above. I
have another experiment here, which I think will explain to you more about it.
When the air is pumped from underneath the bladder which is stretched over
this glass, you will see the effect in another shape: the top is quite flat at
present, but I will make a very little motion with the pump, and now look at
it; see how it has gone down, see how it is bent in; you will see the bladder
go in more and more, until, at last, I expect it will be driven in and broken
by the force of the atmosphere pressing upon it. [The bladder at last broke
with a loud report.] Now that was done entirely by the weight of the air
pressing on it, and you can easily understand how that is. The particles that
are piled up in the atmosphere stand upon each other, as these five cubes do;
you can easily conceive that four of these five cubes are resting upon the
bottom one, and if I take that away the others will all sink down. So it is
with the atmosphere; the air that is above is sustained by the air that is
beneath, and when the air is pumped away from beneath them, the change occurs
which you saw when I placed my hand on the air-pump, and which you saw in the
case of the bladder, and which you shall see better here. I have tied over
this jar a piece of sheet India-rubber, and I am now about to take away the
air from the inside of the jar; and if you will watch the India-rubber which
acts as a partition between the air below and the air above – you will see,
when I pump, how the pressure shows itself. See where it is going to: I can
actually put my hand into the jar; and yet this result is only caused by the
great and powerful action of the air above. How beautifully it shows this
curious circumstance!

Here is something that you can have a pull at when I have finished to day.
It is a little apparatus of two hollow brass hemispheres, closely fitted
together, and having connected with it a pipe and a cock, through which we can
exhaust the air from the inside; and although the two halves are so easily
taken apart, while the air is left within, yet you will see, when we exhaust
it by-and-by, no power of any two of you will be able to pull them apart.
Every square inch of surface that is contained in the area of that vessel
sustains fifteen pounds by weight, or nearly so, when the air is taken out,
and you may try your strength presently in seeing whether you can overcome
that pressure of the atmosphere.

Here is another very pretty thing – the boy’s sucker, only refined by the
philosopher. We young ones have a perfect right to take toys and make them
into philosophy, inasmuch as nowadays we are turning philosophy into toys.
Here is a sucker, only it is made of India-rubber. If I clap it upon the
table, you see at once it holds. Why does it hold? I can slip it about, and
yet if I try to pull it up, it seems as if it would pull the table with it. I
can easily make it slip about from place to place, but only when I bring it to
the edge of the table can I get it off. It is only kept down by the pressure
of the atmosphere above; we have a couple of them, and if you take these two
and press them together, you will see how firmly they stick. And, indeed, we
may use them as they are proposed to be used, to stick against windows, or
against walls, where they will adhere for an evening, and serve to hang any
thing on that you want. I think, however, that you boys ought to be shown
experiments that you can make at home; and so here is a very pretty experiment
in illustration of the pressure of the atmosphere. Here is a tumbler of water.
Suppose I were to ask you to turn that tumbler upside down so that the water
should not fall out, and yet not be kept in by your hand, but merely by using
the pressure of the atmosphere; could you do that? Take a wine-glass, either
quite full or half full of water, and put a flat card on the top; turn it
upside down, and then see what becomes of the card and of the water. The air
can not get in because the water, by its capillary attraction round the edge,
keeps it out.

I think this will give you a correct notion of what you may call the
materiality of the air; and when I tell you that that box holds a pound of it,
and this room more than a ton, you will begin to think that air is something
very serious. I will make another experiment to convince you of this positive
resistance. There is that beautiful experiment of the popgun, made so well and
so easily, you know, out of a quill, or a tube, or any thing of that kind,
where we take a slice of potato, for instance, or an apple, and take the tube
and cut out a pellet, as I have now done, and push it to one end. I have made
that end tight; and now I take another piece and put it in: it will confine
the air that is within the tube perfectly and completely for our purpose; and
I shall now find it absolutely impossible by any force of mine to drive that
little pellet close up to the other. It can not be done; I may press the air
to a certain extent, but if I go on pressing, long before it comes to the
second, the confined air will drive the front one out with a force something
like that of gunpowder; for gunpowder is in part dependent upon the same
action that you see here exemplified.

I saw the other day an experiment which pleased me much, as I thought it
would served our purpose here. (I ought to have held my tongue for four or
five minutes before beginning this experiment, because it depends upon my
lungs for success.) By the proper application of air, I expect to be able to
drive this egg out of one cup into the other by the force of my breath; but if
I fail it is in a good cause, and I do not promise success, because I have
been talking more than I ought to do to make the experiment succeed.

[The lecturer here tried the experiment, and succeeded in blowing the egg
from one egg cup to the other.]

You see that the air which I blow goes downward between the egg and the
cup, and makes a blast under the egg, and is thus able to lift a heavy thing;
for a full egg is a very heavy thing for air to lift. If you want to make the
experiment, you had better boil the egg quite hard first, and then you may
very safely try to blow it from one cup to the other, with a little care.

I have now kept you long enough upon this property of the weight of the
air, but there is another thing I should like to mention. You saw the way in
which, in this popgun, I was able to drive the second piece of potato half or
two-thirds of an inch before the first piece started, by virtue of the
elasticity of the air, just as I pressed into the copper bottle the particles
of air by means of the pump. Now this depends upon a wonderful property in the
air, namely, its elasticity, and I should like to give you a good illustration
of this. If I take any thing that confines the air properly, as this membrane,
which also is able to contract and expand so as to give us a measure of the
elasticity of the air, and confine in this bladder a certain portion of air;
and then, if we take the atmosphere off from the outside of it, just as in
these cases we put the pressure on – if we take the pressure off, you will see
how it will then go on expanding and expanding, larger and larger, until it
will fill the whole of this bell jar, showing you that wonderful property of
the air, its elasticity, its compressibility, and expansibility, to an
exceedingly large extent, and which is very essential for the purposes and
services it performs in the economy of creation.

We will now turn to another very important part of our subject, remembering
that we have examined the candle in its burning, and have found that it gives
rise to various products. We have the products, you know, of soot, of water,
and of something else, which you have not yet examined. We have collected the
water, but have allowed the other things to go into the air. Let us now
examine some of these other products.

Here is an experiment which I think will help you in part in this way. We
will put our candle there, and place over it a chimney, thus. I think my
candle will go on burning, because the air passage is open at the bottom and
the top. In the first place, you see the moisture appearing – that you know
about. It is water produced from the candle by the action of the air upon its
hydrogen. But, besides that, something is going out at the top: it is not
moisture – it is not water – it is not condensible; and yet, after all, it has
very singular properties. You will find that the air coming out of the top of
our chimney is nearly sufficient to blow the light out I am holding to it; and
if I put the light fairly opposed to the current, it will blow it quite out.
You will say, that is as it should be, and I am supposing that you think it
ought to do so, because the nitrogen does not support combustion, and ought to
put the candle out, since the candle will not burn in nitrogen. But is there
nothing else there than nitrogen? I must now anticipate – that is to say, I
must use my own knowledge to supply you with the means that we adopt for the
purpose of ascertaining these things, and examining such gases as these. I
will take an empty bottle – here is one – and if I hold it over this chimney,
I shall get the combustion of the candle below sending its results into the
bottle above; and we shall soon find that this bottle contains, not merely an
air that is bad as regards the combustion of a taper put into it, but having
other properties.

Let me take a little quick-lime and pour some common water on to it the
commonest water will do. I will stir it a moment, then pour it upon a piece of
filtering paper in a funnel, and we shall very quickly have a clear water
proceeding to the bottle below, as I have here. I have plenty of this water in
another bottle, but nevertheless I should like to use the lime water that was
prepared before you, so that you may see what its uses are. If I take some of
this beautiful clear lime-water, and pour it into this jar which has collected
the air from the candle, you will see a change coming about. Do you see that
the water has become quite milky? Observe, that will not happen with air
merely. Here is a bottle filled with air; and if I put a little lime-water
into it, neither the oxygen nor the nitrogen, nor any thing else that is in
that quantity of air, will make any change in the lime water. It remains
perfectly clear, and no shaking of that quantity of lime water with that
quantity of air in its common state will cause any change; but if I take this
bottle with the lime-water and hold it so as to get the general products of
the candle in contact with it, in a very short time we shall have it milky.
There is the chalk, consisting of the lime which we used in making the
lime-water, combined with something that came from the candle – that other
product which we are in search of, and which I want to tell you about today.
This is a substance made visible to us by its action, which is not the action
of the lime-water either upon the oxygen or upon the nitrogen, nor upon the
water itself, but it is something new to us from the candle. And then we find
this white powder, produced by the lime-water and the vapor from the candle,
appears to us very much like whitening or chalk, and when examined it does
prove to be exactly the same substance as whitening or chalk. So we are led,
or have been led, to observe upon the various circumstances of this
experiment, and to trace this production of chalk to its various causes, to
give us the true knowledge of the nature of this combustion of the candle – to
find that this substance issuing from the candle is exactly the same as that
substance which would issue from a retort if I were to put some chalk into it
with a little moisture and make it red-hot; you would then find that exactly
the same substance would issue from it as from the candle.

But we have a better means of getting this substance, and in greater
quantity, so as to ascertain what its general characters are. We find this
substance in very great abundance in a multitude of cases where you would
least expect it. All limestones contain a great deal of this gas which issues
from the candle, and which we call carbonic acid. All chalks, all shells, all
corals, contain a great quantity of this curious air. We find it fixed in
these stones, for which reason Dr. Black called it “fixed air” – finding it in
these fixed things like marble and chalk – he called it fixed air because it
lost its quality of air, and assumed the condition of a solid body. We can
easily get this air from marble. Here is a jar containing a little muriatic
acid, and here is a taper which, if I put it into that jar, will show only the
presence of common air. There is, you see, pure air down to the bottom; the
jar is full of it. Here is a substance – marble 18, a very
beautiful and superior marble – and if I put these pieces of marble into the
jar, a great boiling apparently goes on. That, however, is not steam; it is a
gas that is rising up; and if I now search the jar by a candle, I shall have
exactly the same effect produced upon the taper as I had from the air which
issued from the end of the chimney over the burning candle. It is exactly the
same action, and caused by the very same substance that issued from the
candle; and in this way we can get carbonic acid in great abundance – we have
already nearly filled the jar. We also find that this gas is not merely
contained in marble. Here is a vessel in which I have put some common
whitening-chalk which has been washed in water and deprived of its coarser
particles, and so supplied to the plasterer as whitening – here is a large jar
containing this whitening and water; and I have here some strong sulphuric
acid, which is the acid you might have to use if you were to make these
experiments (only, in using this acid with limestone, the body that is
produced is an insoluble substance, whereas the muriatic acid produces a
soluble substance that does not so much thicken the water). And you will seek
out a reason why I take this kind of apparatus for the purpose of showing this
experiment. I do it because you may repeat in a small way what I am about to
do in a large one. You will have here just the same kind of action; and I am
evolving in this large jar carbonic acid exactly the same in its nature and
properties as the gas which we obtained from the combustion of the candle in
the atmosphere. And, no matter how different the two methods by which we
prepare this carbonic acid, you will see, when we get to the end of our
subject, that it is all exactly the same, whether prepared in the one way or
in the other.

[Footnote 18: Marble is a compound of carbonic acid and lime. The
muriatic acid, being the stronger of the two, takes the place of the
carbonic acid, which escapes as a gas, the residue forming muriate of lime
or chloride of calcium.]

We will now proceed to the next experiment with regard to this gas. What is
its nature? Here is one of the vessels full, and we will try it as we have
done so many other gases – by combustion. You see it is not combustible, nor
does it support combustion. Neither, as we know, does it dissolve much in
water, because we collect it over water very easily. Then you know that it has
an effect, and becomes white in contact with lime-water; and when it does
become white in that way, it becomes one of the constituents to make carbonate
of lime or limestone.

The next thing I must show you is that it really does dissolve a little in
water, and therefore that it is unlike oxygen and hydrogen in that respect. I
have here an apparatus by which we can produce this solution. In the lower
part of this apparatus is marble and acid, and in the upper part cold water.
The valves are so arranged that the gas can get from one to the other. I will
set it in action now, and you can see the gas bubbling up through the water,
as it has been doing all night long, and by this time we shall find that we
have this substance dissolved in the water. If I take a glass and draw off
some of the water, I find that it tastes a little acid to the mouth; it is
impregnated with carbonic acid; and if I now apply a little lime-water to it,
that will give us a test of its presence. This water will make the lime water
turbid and white, which is proof of the presence of carbonic acid.

Then it is a very weighty gas; it is heavier than the atmosphere. I have
put their respective weights at the lower part of this table, along with, for
comparison, the weights of the other gases we have been examining:

—Table 3]

A pint of it weighs 16-1/3 grains, and a cubic foot weighs 1-9/10 ounce,
almost two ounces. You can see by many experiments that this is a heavy gas.
Suppose I take a glass containing nothing else but air, and from this vessel
containing the carbonic acid I attempt to pour a little of this gas into that
glass – I wonder whether any has gone in or not. I can not tell by the
appearance, but I can in this way [introducing the taper]. Yes, there it is,
you see; and if I were to examine it by lime-water, I should find it by that
test also. I will take this little bucket, and put it down into the well of
carbonic acid – indeed, we too often have real wells of carbonic acid – and
now, if there is any carbonic acid, I must have got to it by this time, and it
will be in this bucket, which we will examine with a taper. There it is, you
see; it is full of carbonic acid.

There is another experiment by which I will show you its weight. I have
here a jar suspended at one end of a balance – it is now equipoised; but when
I pour this carbonic acid into the jar on the one side which now contains air,
you will see it sink down at once because of the carbonic acid that I pour
into it. And now, if I examine this jar with the lighted taper, I shall find
that the carbonic acid has fallen into it, and it no longer has any power of
supporting the combustion. If I blow a soap bubble, which of course will be
filled with air, and let it fall into this jar of carbonic acid, it will
float. But I shall first of all take one of these little balloons filled with
air. I am not quite sure where the carbonic acid is; we will just try the
depth, and see whereabouts is its level. There, you see, we have this bladder
floating on the carbonic acid; and if I evolve some more of the carbonic acid,
the bladder will be lifted up higher. There it goes; the jar is nearly full,
and now I will see whether I can blow a soap bubble on that and float it in
the same way. [The lecturer here blew a soap bubble and allowed it to fall
into the jar of carbonic acid, when it floated in it midway.] It is floating,
as the balloon floated, by virtue of the greater weight of the carbonic acid
than of the air. And now, having so far given you the history of the carbonic
acid, as to its sources in the candle, as to its physical properties and
weight, when we next meet I shall show you of what it is composed, and where
it gets its elements from.

Lecture VI: Carbon Or
Charcoal – Coal Gas – Respiration And Its Analogy To A

A Lady who honors me by her presence at these lectures has conferred a
still farther obligation by sending me these two candles, which are from
japan, and, I presume, are made of that substance to which I referred in a
former lecture. You see that they are even far more highly ornamented than the
French candles, and, I suppose, are candles of luxury, judging from their
appearance. They have a remarkable peculiarity about them, – namely, a hollow
wick, – that beautiful peculiarity which Argand introduced into the lamp and
made so valuable. To those who receive such presents from the East, I may just
say that this and such like materials gradually undergo a change which gives
them on the surface a dull and dead appearance; but they may easily be
restored to their original beauty if the surface be rubbed with a clean cloth
or silk handkerchief, so as to polish the little rugosity or roughness: this
will restore the beauty of the colors. I have so rubbed one of these candles,
and you see the difference between it and the other which has not been
polished, but which may be restored by the same process. Observe, also, that
these moulded candles from Japan are made more conical than the moulded
candles in this part of the world.

I told you, when we last met, a good deal about carbonic acid. We found by
the lime-water test that when the vapor from the top of the candle or lamp was
received into bottles and tested by this solution of lime-water (the
composition of which I explained to you, and which you can make for
yourselves), we had that white opacity which was in fact calcareous matter,
like shells and corals, and many of the rocks and minerals in the earth. But I
have not yet told you fully and clearly the chemical history of this
substance, carbonic acid, as we have it from the candle, and I must now resume
that subject. We have seen the products, and the nature of them, as they issue
from the candle. We have traced the water to its elements, and now we have to
see where are the elements of the carbonic acid supplied by the candle. A few
experiments will show this. You remember that when a candle burns badly it
produces smoke; but if it is burning well there is no smoke. And you know that
the brightness of the candle is due to this smoke, which becomes ignited. Here
is an experiment to prove this: so long as the smoke remains in the flame of
the candle and becomes ignited, it gives a beautiful light, and never appears
to us in the form of black particles. I will light some fuel which is
extravagant in its burning. This will serve our purpose – a little turpentine
on a sponge. You see the smoke rising from it, and floating into the air in
large quantities; and remember now, the carbonic acid that we have from the
candle is from such smoke as that. To make that evident to you, I will
introduce this turpentine burning on the sponge into a flask where I have
plenty of oxygen, the rich part of the atmosphere, and you now see that the
smoke is all consumed. This is the first part of our experiment; and now, what
follows? The carbon which you saw flying off from the turpentine flame in the
air is now entirely burned in this oxygen, and we shall find that it will, by
this rough and temporary experiment, give us exactly the same conclusion and
result as we had from the combustion of the candle. The reason why I make the
experiment in this manner is solely that I may cause the steps of our
demonstration to be so simple that you can never for a moment lose the train
of reasoning, if you only pay attention. All the carbon which is burned in
oxygen, or air, comes out as carbonic acid, while those particles which are
not so burned show you the second substance in the carbonic acid, – namely,
the carbon – that body which made the flame so bright while there was plenty
of air, but which was thrown off in excess when there was not oxygen enough to
burn it.

I have also to show you a little more distinctly the history of carbon and
oxygen in their union to make carbonic acid. You are now better able to
understand this than before, and I have prepared three or four experiments by
way of illustration. This jar is filled with oxygen, and here is some carbon
which has been placed in a crucible for the purpose of being made red-hot. I
keep my jar dry, and venture to give you a result imperfect in some degree, in
order that I may make the experiment brighter. I am about to put the oxygen
and the carbon together. That this is carbon (common charcoal pulverized) you
will see by the way in which it burns in the air [letting some of the red hot
charcoal fall out of the crucible]. I am now about to burn it in oxygen gas,
and look at the difference. It may appear to you at a distance as if it were
burning with a flame; but it is not so. Every little piece of charcoal is
burning as a spark, and while it so burns it is producing carbonic acid. I
specially want these two or three experiments to point out what I shall dwell
upon more distinctly by-and-by – that carbon burns in this way, and not as a

Instead of taking many particles of carbon to burn, I will take a rather
large piece, which will enable you to see the form and size, and to trace the
effects very decidedly. Here is the jar of oxygen, and here is the piece of
charcoal, to which I have fastened a little piece of wood, which I can set
fire to, and so commence the combustion, which I could not conveniently do
without. You now see the charcoal burning, but not as a flame (or if there be
a flame it is the smallest possible one, which I know the cause of, namely,
the formation of a little carbonic oxide close upon the surface of the
carbon). It goes on burning, you see, slowly producing carbonic acid by the
union of this carbon or charcoal (they are equivalent terms) with the oxygen.
I have here another piece of charcoal, a piece of bark, which has the quality
of being blown to pieces – exploding – as it burns. By the effect of the heat
we shall reduce the lump of carbon into particles that will fly off; still
every particle, equally with the whole mass, burns in this peculiar way – it
burns as a coal and not like a flame. You observe a multitude of little
combustions going on, but no flame. I do not know a finer experiment than this
to show that carbon burns with a park.

Here, then, is carbonic acid formed from its elements. It is produced at
once; and if we examined it by lime-water you will see that we have the same
substance which I have previously described to you. By putting together 6
parts of carbon by weight (whether it comes from the flame of a candle or from
powdered charcoal) and 16 parts of oxygen by weight, we have 22 parts of
carbonic acid; and, as we saw last time, the 22 parts of carbonic acid
combined with 28 parts of lime, product common carbonate of lime. If you were
to examine an oyster-shell and weigh the component parts, you would find that
every 50 parts would give 6 of carbon and 16 of oxygen combined with 28 of
lime. However, I do not want to trouble you with these minutiae; it is only
the general philosophy of the matter that we can now go into. See how finely
the carbon is dissolving away [pointing to the lump of charcoal burning
quietly in the jar of oxygen]. You may say that the charcoal is actually
dissolving in the air round about; and if that were perfectly pure charcoal,
which we can easily prepare, there would be no residue whatever. When we have
a perfectly cleansed and purified piece of carbon, there is no ash left. The
carbon burns as a solid dense body, that heat alone can not change as to its
solidity, and yet it passes away into vapor that never condenses into solid or
liquid under ordinary circumstances; and what is more curious still is the
fact that the oxygen does not change in its bulk by the solution of the carbon
in it. Just as the bulk is at first, so it is at last, only it has become
carbonic acid.

There is another experiment which I must give you before you are fully
acquainted with the general nature of carbonic acid. Being a compound body,
consisting of carbon and oxygen, carbonic acid is a body that we ought to be
able to take asunder. And so we can. As we did with water, so we can with
carbonic acid – take the two parts asunder. The simplest and quickest way is
to act upon the carbonic acid by a substance that can attract the oxygen from
it, and leave the carbon behind. You recollect that I took potassium and put
it upon water or ice, and you saw that it could take the oxygen from the
hydrogen. Now, suppose we do something of the same kind here with this
carbonic acid. You know carbonic acid to be a heavy gas. I will not test it
with lime-water, as that will interfere with our subsequent experiments, but I
think the heaviness of the gas and the power of extinguishing flame will be
sufficient for our purpose. I introduce a flame into the gas, and you will see
whether it will be put out. You see the light is extinguished. Indeed, the gas
may, perhaps, put out phosphorus, which you know has a pretty strong
combustion. Here is a piece of phosphorus heated to a high degree. I introduce
it into gas, and you observe the light is put out, but it will take fire again
in the air, because there it re-enters into combustion. Now let me take a
piece of potassium, a substance which even at common temperatures can act upon
carbonic acid, though not sufficiently for our present purpose, because it
soon gets covered with a protecting coat; but if we warm it up to the burning
point in air, as we have a fair right to do, and as we have done with
phosphorus, you will see that it can burn in carbonic acid; and if it burns,
it will burn by taking oxygen, so that you will see what is left behind. I am
going, then, to burn this potassium in the carbonic acid, as a proof of the
existence of oxygen in the carbonic acid. [In the preliminary process of
heating the potassium exploded.] Sometimes we get an awkward piece of
potassium that explodes, or something like it, when it burns. I will take
another piece, and now that it is heated I introduce it into the jar, and you
perceive that it burns in the carbonic acid – not so well as in the air,
because the carbonic acid contains the oxygen combined; but it does burn, and
takes away the oxygen. If I now put this potassium into water, I find that
besides the potash formed (which you need not trouble about) there is a
quantity of carbon produced. I have here made the experiment in a very rough
way, but I assure you that if I were to make it carefully, devoting a day to
it instead of five minutes, we should get all the proper amount of charcoal
left in the spoon, or in the place where the potassium was burned, so that
there could be no doubt as to the result. Here, then, is the carbon obtained
from the carbonic acid, as a common black substance; so that you have the
entire proof of the nature of carbonic acid as consisting of carbon and
oxygen. And now I may tell you, that whenever carbon burns under common
circumstances it produces carbonic acid.

Suppose I take this piece of wood, and put it into a bottle with lime
water. I might shake that lime-water up with wood and the atmosphere as long
as I pleased, it would still remain clear as you see it; but suppose I burn
the piece of wood in the air of that bottle. You, of course, know I get water.
Do I get carbonic acid? [The experiment was performed.] There it is, you see
that is to say, the carbonate of lime, which results from carbonic acid, and
that carbonic acid must be formed from the carbon which comes from the wood,
from the candle, or any other thing. Indeed, you have yourselves frequently
tried a very pretty experiment, by which you may see the carbon in wood. If
you take a piece of wood, and partly burn it, and then blow it out, you have
carbon left. There are things that do not show carbon in this way. A candle
does not so show it, but it contains carbon. Here also is a jar of coal gas,
which produces carbonic acid abundantly; you do not see the carbon, but we can
soon show it to you. I will light it, and as long as there is any gas in the
cylinder it will go on burning. You see no carbon, but you see a flame, and
because that is bright it will lead you to guess that there is carbon in the
flame. But I will show it to you by another process. I have some so the same
gas in another vessel, mixed with a body that will burn the hydrogen of the
gas, but will not burn the carbon. I will light them with a burning taper, and
you perceive the hydrogen is consumed, but not the carbon, which is left
behind as a dense black smoke. I hope that by these three or four experiments
you will learn to see when carbon is present, and understand what are the
products of combustion when gas or other bodies are thoroughly burned in the

Before we leave the subject of carbon, let us make a few experiments and
remarks upon its wonderful condition as respects ordinary combustion. I have
shown you that the carbon, in burning burns only as a solid body, and yet you
perceive that, after it is burned, it ceases to be a solid. There are very few
fuels that act like this. It is, in fact, only that great source of fuel, the
carbonaceous series, the coals, charcoals, and woods, that can do it. I do not
know that there is any other elementary substance besides carbon that burns
with these conditions; and if it had not been so, what would happen to us?
Suppose all fuel had been like iron, which, when it burns, burns into a solid
substance. We could not then have such a combustion as you have in this
fireplace. Here also is another kind of fuel which burns very-well as, if not
better, than carbon – so well, indeed, as to take fire of itself when it is in
the air, as you see [breaking a tube full of lead pyrophorus]. This substance
is lead, and you see how wonderfully combustible it is. It is very much
divided, and is like a heap of coals in the fireplace; the air can get to its
surface and inside, and so it burns. But why does it burn in that way now,
when it is lying in a mass? [emptying the contents of the tube in a heap on to
a plate of iron.] Simply because the air can not get to it. Though it can
produce a great heat, the great heat which we want in our furnaces and under
our boilers, still that which is produced can not get away from the portion
which remains unburned underneath, and that portion, therefore, is prevented
from coming in contact with the atmosphere, and can not be consumed. How
different is that from carbon! Carbon burns just in the same way as this lead
does, and so gives an intense fire in the furnace, or wherever you choose to
burn it; but then the body produced by its combustion passes away, and the
remaining carbon is left clear. I showed you how carbon went on dissolving in
the oxygen, leaving no ash, whereas here [pointing to the heap of pyrophorus]
we have actually more ash than fuel, for it is heavier by the amount of the
oxygen which has united with it. Thus you see the difference between carbon
and lead or iron – if we choose iron, which gives so wonderful a result in our
applications of this fuel, either as light or heat. If, when the carbon burnt,
the product went off as a solid body, you would have had the room filled with
an opaque substance, as in the case of the phosphorus; but when carbon burns,
every thing passes up into the atmosphere. It is in a fixed, almost
unchangeable condition before the combustion; but afterward it is in the form
of gas, which it is very difficult (though we have succeeded) to produce in a
solid or liquid state.

Now I must take you to a very interesting part of our subject – to the
relation between the combustion of a candle and that living kind of combustion
which goes on within us. In every one of us there is a living process of
combustion going on very similar to that of a candle, and I must try to make
that plain to you. For it is not merely true in a poetical sense – the
relation of the life of man to a taper; and if you will follow, I think I can
make this clear. In order to make the relation very plain, I have devised a
little apparatus which we can soon build up before you. Here is a board, and a
groove cut in it, and I can close the groove at the top part by a little
cover; I can then continue the groove as a channel by a glass tube at each
end, there being a free passage through the whole. Suppose I take a taper or
candle (we can now be liberal in our use of the word “candle,” since we
understand what it means), and place it in one of the tubes; it will go on,
you see, burning very well. You observe that the air which feeds the flame
passes down the tube at one end, then goes along the horizontal tube, and
ascends the tube at the other end in which the taper is placed. If I stop the
aperture through which the air enters, I stop combustion, as you perceive. I
stop the supply of air, and consequently the candle goes out. But now what
will you think of this fact? In a former experiment I showed you the air going
from one burning candle to a second candle. If I took the air proceeding from
another candle, and sent it down by a complicated arrangement into this tube,
I should put this burning candle out. But what will you say when I tell you
that my breath will put out the candle? I do not mean by blowing at all, but
simply that the nature of my breath is such that a candle can not burn in it.
I will now hold my mouth over the aperture, and without blowing the flame in
any way, let no air enter the tube but what comes from my mouth. You see the
result. I did not blow the candle out. I merely let the air which I expired
pass into the aperture, and the result was that the light went out for want of
oxygen, and for no other reason. Something or other – namely, my lungs – had
taken away the oxygen from the air and there was no more to supply combustion
of the candle. It is, I think, very pretty to see the time it takes before the
bad air which I throw into this part of the apparatus has reached the candle.
The candle at first goes on burning, but so soon as the air has had time to
reach it, it goes out. And now I will show you another experiment, because
this is an important part of our philosophy. Here is a jar which contains
fresh air, as you can seen by the circumstance of a candle or gas light
burning it. I make it close for a little time, and by means of a pipe I get my
mouth over it so that I can inhale the air. By putting it over water, in the
way that you see, I am able to draw up this air (supposing the cork to be
quite tight), take it into my lungs, and throw it back into the jar: we can
then examine it, and see the result. You observe, I first take up the air, and
then throw it back, as is evident from the ascent and descent of the water;
and now, by putting a taper into the air, you will see the state in which it
is, by the light being extinguished. Even one inspiration, you see, has
completely spoiled this air, so that it is no use my trying to breathe it a
second time. Now you understand the ground of the impropriety of many of the
arrangements among the houses of the poorer classes, by which the air is
breathed over and over again for the want of a supply, by means of proper
ventilation, sufficient to produce a good result. You see how bad the air
becomes by a single breathing, so that you can easily understand how essential
fresh air is to us.

To pursue this a little farther, let us see what will happen with lime
water. Here is a globe which contains a little lime-water, and it is so
arranged as regards the pipes, as to give access to the air within, so that we
can ascertain the effect of respired or unrespired air upon it. Of course I
can either draw in air (through A), and so make the air that feeds my lungs go
through the lime-water, or I can force the air out of my lungs through the
tube (B), which goes to the bottom, and so show its effect upon the lime
water. You will observe that however long I draw the external air into the
lime-water and then through it to my lungs, I shall produce no effect upon the
water – it will not make the lime-water turbid; but if I throw the air from my
lungs through the lime-water several times is succession, you see how white
the milky the water is getting showing the effect which expired air has had
upon it; and now you begin to know that the atmosphere which we have spoiled
by respiration is spoiled by carbonic acid, for you see it here in contact
with the lime-water.

I have here two bottles, one containing lime-water and the other common
water, and tubes which pass into the bottles and connect them. The apparatus
is very rough, but it is useful notwithstanding. If I take these two bottles,
inhaling here and exhaling there, the arrangement of the tubes will prevent
the air going backward. The air coming in will go to my mouth and lungs, and
in going out will pass through the lime-water, so that I can go on breathing,
and making an experiment very refined in its nature and very good in its
results. You will observe that the good air has done nothing to the
lime-water; in the other case, nothing has come to the lime-water but my
respiration, and you see the difference in the two cases.

Let us now go a little farther. What is all this process going on within us
which we can not do without, either day or night, which is provided for by the
Author of all things that He has arranged that it shall be independent of all
will? If we restrain our respiration, as we can to a certain extent, we should
destroy ourselves. When we are asleep the organs of respiration and the parts
that are associated with them still go on with their action, so necessary is
this process of respiration to us, this contact of the air with the lungs. I
must tell you, in the briefest possible manner, what this process is. We
consume food; the food goes through that strange set of vessels and organs
within us, and is brought into various parts of the system, into the digestive
parts especially; and alternately the portion which is so changed is carried
through our lungs by one set of vessels, while the air that we inhale and
exhale is drawn into and thrown out of the lungs by another set of vessels, so
that the air and the food come close together, separated only by an
exceedingly thin surface; the air can thus act upon the blood by this process,
producing precisely the same results in kind as we have seen in the case of
the candle. The candle combines with parts of the air, forming carbonic acid,
and evolves heat; so in the lungs there is this curious, wonderful change
taking place. The air entering, combines with the carbon (not carbon in a free
state, but, as in this case, placed ready for action at the moment), and makes
carbonic acid and is so thrown out into the atmosphere, and thus this singular
result takes place; we may thus look upon the food as fuel. Let me take that
piece of sugar, which will serve my purpose. It is a compound of carbon,
hydrogen, and oxygen, similar to a candle, as containing the same elements,
though not in the same proportion, the proportions being as shown in this

—Table 4]

This is, indeed, a very curious thing, which you can well remember, for the
oxygen and hydrogen are in exactly the proportions which form water, so that
sugar may be said to be compounded of 72 parts of carbon and 99 parts of
water; and it is the carbon in the sugar that combines with the oxygen carried
in by the air in the process of respiration – so making us like candles –
producing these actions, warmth, and far more wonderful results besides, for
the sustenance of the system, by a most beautiful and simple process. To make
this still more striking, I will take a little sugar; or, to hasten the
experiment, I will use some sirup, which contains about three-fourths of sugar
and a little water. If I put a little oil of vitriol on it, it takes away the
water, and leaves the carbon in a black mass. [The lecturer mixed the two
together.] You see how the carbon is coming out, and before long we shall have
a solid mass of charcoal, all of which has come out of sugar. Sugar, as you
know, is food, and here we have absolutely a solid lump of carbon where you
would not have expected it. And if I make arrangements so as to oxidize the
carbon of sugar we shall have a much more striking result. Here is sugar, and
I have here an oxidizer – a quicker one than the atmosphere; and so we shall
oxidize this fuel by a process different from respiration in its form, though
not different in its kind. It is the combustion of the carbon by the contact
of oxygen which the body has supplied to it. If I set this into action at
once, you will see combustion produced. Just what occurs in my lungs – taking
in oxygen from another source, namely, the atmosphere – takes place here by a
more rapid process.

You will be astonished when I tell you what this curious play of carbon
amounts to. A candle will burn some four, five, six, or seven hours. What,
then, must be the daily amount of carbon going up into the air in the way of
carbonic acid! What a quantity of carbon must go from each of us in
respiration! What a wonderful change of carbon must take place under these
circumstances of combustion or respiration! A man in twenty-four hours
converts as much as seven ounces of carbon into carbonic acid; a milch cow
will convert seventy ounces, and a horse seventy-nine ounces, solely by the
act of respiration. That is, the horse in twenty-four hours burns seventy nine
ounces of charcoal, or carbon, in his organs of respiration to supply his
natural warmth in that time. All the warm-blooded animals get their warmth in
this way, by the conversion of carbon, not in a free state, but in a state of
combination. And what an extraordinary notion this gives us of the alterations
going on in our atmosphere. As much as 5,000,000 pounds, or 548 tons, of
carbonic acid is formed by respiration in London alone in twenty four hours.
And where does all this go? Up into the air. If the carbon had been like the
lead which I showed you, or the iron which, in burning, produces a solid
substance, what would happen? Combustion could not go on. As charcoal burns it
becomes a vapor and passes off into the atmosphere, which is the great
vehicle, the great carrier for conveying it away to other places. Then what
becomes of it? Wonderful is it to find that the change produced by
respiration, which seems so injurious to us (for we can not breathe air twice
over), is the very life and support of plants and vegetables that grow upon
the surface of the earth. It is the same also under the surface, in the great
bodies of water; for fishes and other animals respire upon the same principle,
though not exactly by contact with the open air.

Such fish as I have here [pointing to a globe of goldfish] respire by the
oxygen which is dissolved from the air by the water, and form carbonic acid,
and they all move about to produce the one great work of making the animal and
vegetable kingdoms subservient to each other. And all the plants growing upon
the surface of the earth, like that which I have brought here to serve as an
illustration, absorb carbon; these leaves are taking up their carbon from the
atmosphere to which we have given it in the form of carbonic acid, and they
are growing and prospering. Give them a pure air like ours, and they could not
live in it; give them carbon with other matters, and they live and rejoice.
This piece of wood gets all its carbon, as the trees and plants get theirs,
from the atmosphere, which, as we have seen, carries away what is bad for us
and at the same time good for them – what is disease to the one being health
to the other. So are we made dependent not merely upon our fellow-creatures,
but upon our fellow-existers, all Nature being tied together by the laws that
make one part conduce to the good of another.

There is another little point which I must mention before we draw to a
close – a point which concerns the whole of beauty of the taper by making your
deeds honorable and effectual in the discharge of your duty to your

[Footnote 19: Lead pyrophorus is made by heating dry tartrate of lead in
a glass tube (closed at one end, and drawn out to a fine point at the other)
until no more vapors are evolved. The open end of the tube is then to be
sealed before the blowpipe. When the tube is broken and the contents shaken
out into the air, they burn with a red flash.]


Scientific papers: physics, chemistry, astronomy, geology, with
introductions, notes and illustrations
. New York, P. F. Collier & son
[c1910], Harvard classics ; no.XXX.

This text is in the public domain