284 The American Geologist. Novemb.r, 189;^ 
ready to meet a congress of nations, to rejoice witli tiie chemist 
upon the issue of his task. 
It is well known that chemical labor has not been barren of re- 
turns. The products of chemical action, numliering thousands of 
thousands, have l)een sifted and measured and weighed. If you 
ask what happens in a common chemical change you can obtain 
direct answers. When coal burns in the air, how much oxygen 
is used up can be stated with a degree of exactness true to the 
first decimal of mass, perhaps to the second, yet questionalMe in 
the third. How much carbonic acid is made can be told in weight 
and in volume with approaching exactness. How much heat this 
chemical action is worth, how much light, how much electro-mo- 
tive force, what train-load of cars it can carry, how long it can 
make certain wheels go round, — for these questions chemists and 
physicists are ready. With how many metals carbonic acid will 
unite, how many others it can make into carbonates, into what 
classes of molecules a certain larger fragment of carbonic acid can 
be formed, the incomplete records of these things already run 
through a great many volumes. These carboxylic bodies are open 
to productive studies, stimulated l\y various sorts of inquiry and 
demands of life. Such have been the gatherings of research. 
They have been slowly drawn into order, more slowly interpreted 
in meaning. The advance has been constant, deliberate, some- 
times in doubt, always persisting and gradually gaining firmer 
ground. So chemistry has reached the period of dcjinlliou. Its 
guiding theory has come to be realized. 
" The atomic theory " has more and more plainly appeared to 
be the central and vital truth of chemical science. As a working 
hypothesis it has directed abstruse research through difficult ways 
to open accomplishment in vivid reality. As a system of knowl- 
edge, it has more than kept pace with the rate of invention. Asa 
philosophy, it is in touch with profound truth in physics, in the 
mineral kingdom, and in the functions of living bodies. As a lan- 
guage it has been a necessity of man in dealing with chemical 
events. Something might have been done, no doubt, without it, 
had it been possible to keep it out of the chemical mind. But 
with a knowledge of the primary elements of matter, as held at 
the beginning of this century, some theory of chemical atoms was 
inevitable. And whatever theory might have l>een adapted, its 
use in investigation would have drawn it with a certainty into the 
