THE NEW CHEMISTRY 



401 



those of another molecule, or molecules, brought within its sphere of 

 action ? Here is another question which can only be answered after 

 much experimental evidence has been accumulated. Now, these ques- 

 tions, I make bold to say, are the direct outcome of the dualism of 

 Berzelius, modified by the unitary chemistry of Dumas and his fol- 

 lowers. 



If we glance back on the development of the two theories, the 

 course of which I have endeavored to outline, we find that both began 

 with a purely qualitative study of reactions, but that it was only when 

 to this had been added the careful use of weights and measures that 

 any solid advance became possible. Further, we find that the older 

 theory was founded chiefly on a study of reactions, while that which 

 was broached after the time of Lavoisier was founded most largely on 

 a study of composition. With the phlogisteans function was of para- 

 mount importance ; with the dualists composition was all. The mod- 

 ern theories, which have been developed from these, have attempted, 

 with varying success, to combine both considerations. And if we 

 examine the latest advances of theoretical chemistry we still find it at 

 work on these two lines of advance. The composition of chemical 

 compounds is studied by the majority of chemists ; but the general 

 laws of action of chemical force itself have of late received most im- 

 portant elucidation. 



Again, if we look to the " lines of advance along which dynamical 

 science is working its way to undermine, at least, the outworks of 

 chemistry," we can distinguish two, essentially the same, lines as were 

 used by the two classes, whose theories I have dealt with in this paper. 

 " One is conducted by the help of the hypothesis that bodies consist of 

 molecules in motion, and it seeks to determine the structure of the 

 molecules and the nature of their motion from the phenomena of por- 

 tions of matter of sensible size. The other line of advance, that of 

 thermo-dynamics, makes no hypothesis about the ultimate structure of 

 bodies, but deduces relations among observed phenomena by means 

 of two general principles, the conservation of energy and its tendency 

 toward diffusion." (Clerk Maxwell, " South Kensington Science Con- 

 ferences," 1876, p. 145.) 



I have thus sought to substantiate the claim of the new chemistry 

 to be a development of the old. I believe that, if this claim is granted, 

 the conclusion to be drawn must be, not that the old is better, but that 

 to return to that which is admittedly an early stage of development 

 would be to misread all the teachings even of the old chemistry itself. 



In examining the progress of Science we see that she is not afraid 

 to retrace her steps, and that she is able to retain and develop all that 

 is probably true, while rejecting all that is proved to be false ; and, 

 when we learn that she does this, can we hesitate to find in her history 

 the " promise and potency " of a mighty future ? Popular Science 

 Review . 



vol. xvii. 26 



