258 - EVOLUTION AND THE PRESENT AGE 
in and chemistry entered upon a career of achievement 
too vast for the imagination to compass. In my own 
mind familiarity has not yet begun to deaden the feel- 
ing of stupefied amazement when I reflect that scarcely 
a century has elapsed since Dr. Priestley informed man- 
kind of the existence of oxygen. At the present day man 
has created in the laboratory more than one hundred 
thousand distinct substances which never existed before 
and never would havecome into existence but for the hu- 
man mind. Weare now able to deal with one hundred 
thousand kinds of matter which were absent from the 
world of our great-grandfathers. These new material 
creations have their properties, like other kinds of matter. 
They react upon incident forces, each after its peculiar 
manner. They are useful in countless ways in the 
industrial arts, they furnish us with thousands of new 
medicines, and here and there they enable our spiritual 
vision to penetrate a little farther than formerly into 
the habits and behaviour of the myriad swinging and 
dancing atoms that taken together make the visible 
world. 
I have said enough for my present purpose about 
that creation of motor energy, alike in regard to masses 
and in regard to molecules and atoms, which is the 
leading characteristic of the present age on its ma- 
terial side. We have now to consider what I called 
its chief characteristic on the intellectual or spiritual 
side, namely, the unification of nature. I said at the 
outset that this phrase is not altogether satisfactory, 
and perhaps we might substitute for it the doctrine of 
evolution. At all events, I wish to point out that the 
doctrine of evolution amounts to pretty much the same 
thing as the unification of nature. In order to illustrate 
ee 
