162 
boys’ department. 
from the air. Carbonic acid gas, is not like 
oxygen and nitrogen, a. simple, or elementary sub¬ 
stance. By these terms, I mean a body which is 
not combined with any other. This gas is a com¬ 
pound of charcoal (which chemists call carbon), 
and of oxygen. Carbon is one of the elementary 
bodies, and enters largely into the composition of 
all vegetables, as well as of animals. When ani¬ 
mal, or vegetable matter is consumed, as wood and 
hair, the carbon it contains, unites with a certain 
proportion of the oxygen of the air, and forms the 
gas called carbonic acid. Now, as a given bulk of 
this gas is much heavier than the same quantity of 
atmospheric air, you would naturally suppose that 
it would all settle upon the earth by the force of 
gravity; but such is not the case. On the contrary, 
it rises, when formed near the earth, and diffuses 
itself through the body~of the atmosphere, even far 
above the tops of the highest mountains; for, the 
gases, composing the atmosphere, are governed by a 
law which compels them to mingle together, no matter 
how great the difference in their densities, or weights, 
uniting merely by mechanical mixture, omd not chem¬ 
ically combined. This is one of the innumerable 
illustrations which science affords, of the agency 
and controlling power of Supreme Wisdom. Were 
the carbonic acid, which is so widely diffused 
throughout the vast regions of the air, to be drawn 
downward by the same force that operates on solid 
bodies, the immediate suffocation and death of every 
breathing creature, would be the inevitable result! 
(a) You have Undoubtedly heard of deaths pro¬ 
duced by vessels of burning charcoal, in a close 
sleeping apartment. In such cases, it is the car¬ 
bonic acid that destroys life. I do not think you 
ever heard' of any one, possessing even a slight 
knowledge of chemistry, who has been a victim to 
this suicidal method- of procuring warmth. This 
body is called an acid, because, although existing in 
a gaseous state, it yet possesses properties peculiar 
to all acids. I shall say nothing further about it at 
present, only to advise you to remember what has 
been said; and not to suppose, that, because there 
are only about one part of it in two thousand parts 
of air, that it is deserving of but little notice. One 
of the peculiarities, or rather beauties of nature’s 
doings, is to produce vast results by simple means 
and apparently inferior agencies. 
There is another constituent, which has not un¬ 
til recently been admitted by chemists, into the 
family of the gases, of which the atmosphere is com¬ 
posed. This is ammonia , a gas which, like car¬ 
bonic acid, is a compound. It is formed by the 
union of nitrogen and hydrogen. The former has 
been described, and the latter I will defer, until I 
treat of water. Ammonia is a colorless gas, and 
when in a pure, or concentrated state, it is charac¬ 
terized by a remarkable pungency. Smelling bot¬ 
tles are filled with a solution, or substance, which 
emits this gas ; after once inhaling it, you will not 
be liable to mistake its odor. The reason why we 
do not smell ammonia, at all times, in the air, is, be¬ 
cause its proportion is so small. It is very soluble 
in water which will absorb more than 500 times its 
own bulk, and when thus saturated, it is called spir¬ 
its of hartshorn , or aqua ammonia. As it is always 
present in rain water, snow, and hail, it is often per- 
ceptible to the smell after a shower. 
In addition to the constituents already described, 
watery vapor is always present in the air, though in 
variable proportions. There is usually more va¬ 
por in the atmosphere in warm, than in cold, weath¬ 
er. It is produced, as you are probably aware, 
by the constant evaporation of water from the 
surface of the earth and the ocean, and from rivers, 
seas, lakes, &c. When -the air becomes saturated, 
or filled with vapor, a slight cooling causes it to 
condense in the form of clouds; and when it be¬ 
comes so much condensed that the air can no longer 
bear it up, it falls to the earth in the form of rain, 
hail, or snow. A good illustration of this con¬ 
densation is seen, when an earthen, or glass vessel 
is filled with cold water, in a warm atmosphere. 
The outer surface of the vessel, in becoming cooler 
than the surrounding air, causes the vapor, which 
comes in contact with it, to condense, and thus it is 
covered with a watery film, sometimes called sweat. 
Vapor is not a simple or elementary substance, but is 
principally composed of two gases, which will be 
described'when J take up the subject of water. 
There are numerous other ingredients in the air, 
which has been called “ accidental constituents ;” 
as nitric acid (a combination of nitrogen and oxy¬ 
gen), which is always present after a thunder 
shower; dust, after a long continuance of dry 
weather; the vapor of sea water and its constitu¬ 
ents, near the sea coast; the odor of trees, 
plants, flowers, or fruits; and some compounds of 
carbon, phosphorus, and sulphur, with hydrogen, 
which are found in the vicinity of marshes. In my 
next letter 1 shall treat of water. 
J. McKinstry. 
Greenport, Columbia Co., N. Y. 
(a) Were the gases of the atmosphere separately 
to obey the natural law of gravitation, like all other 
bodies with which we are acquainted, the ocean and 
lower parts of the earth would be covered with a 
stratum of carbonic acid gas, 15 or 20 feet in 
thickness. The oxygen and nitrogen, too, instead 
of being uniformly mixed throughout the whole 
atmosphere, as at present, would form two immense 
layers, of unequal thickness, arranged in the order of 
their densities, the oxygen below and the nitrogen 
above. In such a state of things, animal and 
vegetable existence would be out of the question; 
and all the phenomena of combustion and oxyda- 
tion, would be increased, over the chief part of the 
earth’s surface, in ten-fold power. 
A Lesson in Engineering. —“My son,” said 
an engineer, “ come hither; I want to show you 
something.” 
“ Well, father, what is it I” 
“Do you see this kettle bail ?” 
“ Yes.” 
“ There”—standing it up perpendicularly on the 
table—“ do you see that I” 
“Yes, sir.” 
“Well, then, ” laying it down upon the table, “ do 
you see that? Well, it is no farther round that 
bail as it lies flat, than it is over it when it stands 
up. So, when you come to a hill, remember it 
may be no farther around the base than over the 
summit, while it is a great deal easier.”— Exchange 
Paper. 
