GEORGE FREDERICK BARKER. xix 



That the taking up of the teaching of physics by Dr. Barker did 

 not prevent a continued interest in chemical studies is shown by his 

 serving as the chairman of the sub-section of chemistry of the Amer- 

 ican Association in 1876, when he deHvered a notable address on 

 '' The Molecule and the Atom." In this he points out the impor- 

 tance of considering the energy interchanges in chemical reactions, 

 a matter which up to that time had been more or less neglected. 

 Even as late as 1891, he was honored by being made president of 

 the American Chemical Society, and delivered an address on the 

 " Borderland between Physics and Chemistry," in which he dealt 

 with the necessity for distinguishing the fundamental notion of 

 " mass " from that of " weight." He further showed the rich harvest 

 to be expected in the application of the kinetic theory to solutions,, 

 and concluded by a remarkably clear exposition of what was then 

 known of the nature of electric forces in their relation to chemical 

 actions. In these later years, it has indeed been the field of physical 

 chemistry which has yielded an abundant harvest ; the advances in 

 it have been of the greatest importance to science. Indeed, the 

 electro-physicist of today has even split the one time ultimate chem- 

 ical atom into the more fundamental electrons. We must credit Dr. 

 Barker with a keen appreciation of the directions in which further 

 scientific advances were to be made. 



None the less clear was his prevision of the future of applied 

 science. In this connection the writer must content himself by 

 quoting from a brief paper read at the Saratoga Meeting of the 

 American Association for the Advancement of Science in 1879. 

 The title of the paper was '' On the Conversion of Mechanical 

 energy into Heat by Dynamo Electric Machines." It must be 

 remembered that at the time the paper was read no practical in- 

 candescent electric lamp had been made, and industrial electric 

 development had scarcely begun even with the older arc light. The 

 quotation reads : 



The amount of heat actually obtainable from dynamo electric machines 

 when worked upon a commercial scale, is a question which in the near 

 future is to become of very considerable commercial importance. That 

 electric distribution, at least in our larger cities, is ultimately to be the source 

 of light supply, is already placed beyond a peradventure. But far more than 



