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