ANNUAL ADDRESS OF THE PRESIDENT. LIX 
chemistry. Let us not wonder, then, that it took more than two 
thousand years to perfect the doctrine of atoms as a clew to the 
“mystery of matter.” Democritus invented a mechanical key 
of wonderful ingenuity, but it would not unlock anything that 
could not be unlocked without. it. Newton divined that the 
key must be fitted to the two great wards of chemical attrac- 
tion and chemical repulsion, but still the key would not turn in the 
udamantine lock of Nature. Dalton found that the secret of the 
combination must be sought in wards nicely graduated according to 
certain fixed, definite, and multiple numbers, and, since his day, 
door after door in the chemist’s “chamber of imagery” has seemed 
to swing open at the touch of this talisman. And even, if in the 
next two thousand years, or in the next twenty years, the theory of 
John Dalton should be absorbed in some deeper truth, there will 
still be room in the pantheon of science for the memorial bust of 
the plain Manchester arithmetician, so long as men recall how far 
that little candle, which he lighted with inflammable gas obtained 
in the rudest way from the ponds of Lancashire, has thrown its 
quickening beams across the whole tract of modern chemistry. 
