changing of a word in the sentence may
give expression to an entirely different idea. Reverse the letters in
the word "God," and you get the name of our faithful friend the dog.
Huxley and Tyndall both taught that it was the way that the ultimate
particles of matter are compounded that makes the whole difference
between a cabbage and an oak, or between a frog and a man. It is a hard
proposition. We know with scientific certainty that the difference
between a diamond and a piece of charcoal, or between a pearl and an
oyster-shell, is the way that the particles of carbon in the one case,
and of calcium carbide in the other, are arranged. We know with equal
certainty that the difference between certain chemical bodies, like
alcohol and ether, is the arrangement of their ultimate particles, since
both have the same chemical formula. We do not spell acetic acid,
alcohol, sugar, starch, animal fat, vegetable oils, glycerine, and the
like, with the same letters; yet nature compounds them all of the same
atoms of carbon, hydrogen, and oxygen, but in different proportions and
in different orders.

Chemistry is all-potent. A mechanical mixture of two or more elements
is a simple affair, but a chemical mixture introduces an element of
magic. No conjurer's trick can approach such a transformation as that of
oxygen and hydrogen gases into water. The miracle of turning water into
wine is tame by comparison. Dip plain cotton into a mixture of nitric
and sulphuric acids and let it dry, and we have that terrible explosive,
guncotton. Or, take the cellulose of which cotton is composed, and add
two atoms of hydrogen and one of oxygen, and we have sugar. But we are
to remember that the difference here indicated is not a quantitative,
but a qualitative one, not one affecting bulk, but affecting structure.
Truly chemistry works wonders. Take ethyl alcohol, or ordinary spirits
of wine, and add four more atoms of carbon to the carbon molecule, and
we have the poison carbolic acid. Pure alcohol can be turned into a
deadly poison, not by adding to, but simply by taking from it; take out
one atom of carbon and two of hydrogen from the alcohol molecule, and we
have the poison methyl alcohol. But we are to remember that the
difference here indicated is not a quantitative, but a qualitative one,
not one affecting bulk, but affecting structure.

In our atmosphere we have a mechanical mixture of nitrogen and oxygen,
four parts of nitrogen to one of