32 
POPULAR SCIENCE REVIEW. 
The new system tends more and more to bring chemistry 
under the sphere of general dynamics ; the points of relation 
between chemistry and physics are every day being increased 
in number and in definiteness. The old system, in refusing the 
aid of those generalizations which I have briefly alluded to, 
tends to lessen the points of connection between chemistry and 
general physics, necessitates more or less the treatment of 
chemistry as a detached subject, and, in doing this, opposes the 
advance of that time when the grand idea of the unity of the 
sciences is to be realized. 
The hypotheses, with the use of which the upholders of the 
modern school are taunted by their opponents, have done and 
are doing good work for chemical science. Has not the 
hypothesis of Mendelejeff necessitated the revision of the com- 
bining numbers of some of the rarer metals ? * and have not the 
recent determinations of the specific heats of these metals 
proved that the hypothetical numbers were more correct than 
those which were founded on facts (?) ? 
Has not the “ periodic” hypothesis enabled Mendelejeff to pre- 
dict the discovery of certain new elements, even to tell the 
probable properties of some of these elements ? and has not the 
discovery of gallium at least rendered very probable the 
accuracy of his predictions ? 
Must we give up all these results ? Must we return to mere 
empiricism ? The difference between the old and the new 
chemistry is not a difference in the formulation of certain com- 
pounds ; it does not consist in preferring certain numbers to cer- 
tain other numbers : there is an essential difference in the 
fundamental methods of the two systems. To me it appears 
that the old system is empiric, the new scientific. Empiricism 
must precede science ; but when we have attained to a certain 
degree of accurate knowledge, when we have gained a few far- 
reaching generalizations, to give up these and to return to isolated 
facts is, in my estimation, essentially opposed to the very nature 
of the scientific method. 
I do not mean to assert that the new system is the best 
possible system ; every day its defects are apparent. As 
chemistry advances, it is most evident that the system will 
require to be largely developed and perhaps, in portions, recast. 
Nor do I mean to deny that the old system has some points in 
its favour : there are reactions which can be more simply repre- 
sented in terms of the old than in terms of the new notation. 
But I do think that the principles underlying the old system 
are principles which in their essence are opposed to true 
scientific advance, and that the principles underlying the new 
system are such as permit of great advances being made in the 
future, just as they have aided in the great advances of the past. 
