Outlines of the Earths History | Page 7

vision. They even suggested the
great truth that matter of all kinds is made up of inconceivably small
indivisible bits which they and we term atoms. It is likely that in the
classic days of Greece men began to make simple experiments of a
chemical nature. A century or two after the time of Mohammed, the
Arabians of his faith, a people who had acquired Greek science from
the libraries which their conquests gave them, conducted extensive
experiments, and named a good many familiar chemical products, such
as alcohol, which still bears its Arabic name.
These chemical studies were continued in Europe by the alchemists, a
name also of Arabic origin, a set of inquirers who were to a great extent
drawn away from scientific studies by vain though unending efforts to
change the baser metals into gold and silver, as well as to find a
compound which would make men immortal in the body. By the
invention of the accurate balance, and by patient weighing of the
matters which they submitted to experiment, by the invention of
hypotheses or guesses at truth, which were carefully tested by
experiment, the majestic science of modern chemistry has come forth
from the confused and mystical studies of the alchemists. We have

learned to know that there are seventy or more primitive or apparently
unchangeable elements which make up the mass of this world, and
probably constitute all the celestial spheres, and that these elements in
the form of their separate atoms may group themselves in almost
inconceivably varied combinations. In the inanimate realm these
associations, composed of the atoms of the different substances,
forming what are termed molecules, are generally composed of but few
units. Thus carbonic-acid gas, as it is commonly called, is made up of
an aggregation of molecules, each composed of one atom of carbon and
two of oxygen; water, of two atoms of hydrogen and one of oxygen;
ordinary iron oxide, of two atoms of iron and three of oxygen. In the
realm of organic life, however, these combinations become vastly more
complicated, and with each of them the properties of the substance thus
produced differ from all others. A distinguished chemist has estimated
that in one group of chemical compounds, that of carbon, it would be
possible to make such an array of substances that it would require a
library of many thousand ordinary volumes to contain their names
alone.
It is characteristic of chemical science that it takes account of actions
which are almost entirely invisible. No contrivances have been or are
likely to be invented which will show the observer what takes place
when the atoms of any substance depart from their previous
combination and enter on new arrangements. We only know that under
certain conditions the old atomic associations break up, and new ones
are formed. But though the processes are hidden, the results are
manifest in the changes which are brought about upon the masses of
material which are subjected to the altering conditions. Gradually the
chemists of our day are learning to build up in their laboratories more
and more complicated compounds; already they have succeeded in
producing many of the materials which of old could only be obtained
by extracting them from plants. Thus a number of the perfumes of
flowers, and many of the dye-stuffs which a century ago were extracted
from vegetables, and were then supposed to be only obtainable in that
way, are now readily manufactured. In time it seems likely that
important articles of food, for which we now depend upon the seeds of
plants, may be directly built up from the mineral kingdom. Thus the

result of chemical inquiry has been not only to show us much of the
vast realm of actions which go on in the earth, but to give us control of
many of these movements so that we may turn them to the needs of
man.
Animals and plants were at an early day very naturally the subjects of
inquiry. The ancients perceived that there were differences of kind
among these creatures, and even in Aristotle's time the sciences of
zoölogy and botany had attained the point where there were
considerable treatises on those subjects. It was not, however, until a
little more than a century ago that men began accurately to describe and
classify these species of the organic world. Since the time of Linnæus
the growth of our knowledge has gone forward with amazing swiftness.
Within a century we have come to know perhaps a hundred times as
much concerning these creatures as was learned in all the earlier ages.
This knowledge is divisible into two main branches: in one the
inquirers have taken account of the different species, genera, families,
orders, and classes of living forms with such effect that they