VILLAGE LECTURES.—RO. 4. 
47 
ductive of flame, it would extinguish flame im¬ 
mediately on its being brought in contact with 
it; and therefore, also, so far from encouraging 
that chemical action which goes on during res¬ 
piration of animals, and to which the healthful¬ 
ness of a fine bracing air is owing, it extin¬ 
guishes that chemical action at once, and would 
choke any animal that fell into it; but to this 
point we shall refer again. 
Now, if I prove that the air contains this gas, 
the carbonic acid gas, as it is called, which con¬ 
tains the charcoally part of wood, then I shall 
have proved that the air contains the very sub¬ 
stances which we find in trees and plants, and 
which they take from it in the act of growth, 
and this is the way in which I prove that. The 
carbonic acid gas is recognised not only by its 
extinguishing flame and destroying life, but by 
this curious property, that when united with 
lime it forms a chalky insoluble substance; so 
that if I pour some clear lime water into this 
jar of it, and shake it up to induce the lime of 
the water to unite with the gas, it will become 
white and milky in appearance, owing to the 
formation of this chalky, insoluble substance, 
as you see. Now, if I can pass a quantity of 
common air through some lime water, and the 
lime water, originally clear, becomes milky in 
this way, it will be because it, too, contains car¬ 
bonic acid, and I shall thus have proved that 
there is in the air, a gas which contains the 
very particles of charcoal which our plants and 
trees require for their growth. Of course 
the air contains a very small portion of it, not 
so much as yA-i. of its bulk; because, if it con¬ 
tained much, it would destroy life instead of 
preserving it; and I must, therefore, employ an 
apparatus which enables me to draw a large 
quantity of air through a small quantity of lime 
water; such an apparatus, in fact, as I have 
here, where the wafer below falls out and pulls 
the air in after it, through the lime water in this 
crooked tube; and you see that though clear 
before, it is muddy enough now, owing to the 
formation of chalk in it, or carbonate of lime; 
and I have thus proved that the air contains the 
carbonic acid gas which was necessary to form 
this chalk, contains charcoal—contains the sub¬ 
stance of our plants and trees. 
The air, then, contains charcoal, and gives it 
to plants. The fact is, that carbonic acid gas 
is a compound of charcoal and oxygen; you saw 
it formed when I burned the charcoal in the 
oxygen; and the fact is, that, in the sunshine, 
plants absorb the carbonic acid, take its carbon, 
or charcoal, and give back its oxygen pure to 
the air. But before you can see the beauty of 
this process, for it does appear a really beauti¬ 
ful thing when rightly understood, it is neces¬ 
sary for you to know the properties of these 
two gases. Carbonic acid gas is “ choke damp;” 
it sometimes collects in old wells and pits, and 
would then kill any one who enters them. It is 
heavier than common air, and so sometimes col¬ 
lects in deep places. There are places where 
this gas accumulates on the surface of the earth. 
There is a valley in the island of Java, in the 
bottom of which there is a spring of this gas, 
and accordingly the valley is a lake of carbonic 
acid gas, and it is, in reality, what is called, the 
Valley of Death. Travellers who have visited 
it describe it as an utterly barren basin, with a 
rim of remarkably luxuriant vegetation, and 
the skeletons of animals cover the ground be¬ 
neath ; they had wandered in, been choked by 
the gas and died. There was a skeleton of a 
man lying a little way down the slope; he had 
unwittingly entered the fatal lake of air, been 
intoxicated by breathing it, for it is a narcotic 
poison, and lying down, had died. No one dared 
venture to enter the fatal air to help or recover 
a friend without the certainty of sharing his 
fate. 
Now, wherever oxygen is united with char¬ 
coal, it is forming this deadly destructive gas; 
and every fire that burns, and every dungheap 
as it rots, and every breath that is drawn, is 
simply a uniting of the charcoally substance of 
wood or coal, or straw or food, with the oxygen 
of the air, and is constantly giving out carbonic 
acid gas. And the air, though it contains but 
little proportionally, contains a great deal of 
this gas actually. There is but joVo P art °f 
the air that is carbonic acid gas, but then there 
are 42,000 tons of air resting on every acre of 
the earth’s surface, so that there are actually 
400 lbs. of carbonic acid gas—a quantity con¬ 
taining 100 lbs. of charcoal—in the air over 
every square perch of ground; and this, of 
course, increases with every breath that is 
drawn, and every fire that is burned, so that 
we might suppose, in the course of years, the 
atmosphere would become loaded with this gas, 
and animals would be unable to live in it; and 
no doubt this would ultimately be the case; 
for besides the fires which are thus making the 
air unfit for animal life, animals are rapidly 
making it unfit for themselves. Each of us 
gives out carboni-c acid gas with the air we 
breathe—our lungs are in fact, a little fireplace 
within each of us, where our food is in a great 
1 measure burnt up, and our windpipe is the 
