642 REPORT— 1895. 



their development. The pioneers of our science on whose shoulders we stand — 

 and many of whom are happily still among us — will derive satisfaction from the 

 retrospect, and will admit that their labours have borne goodly fruit. It is not, 

 however, simply for the purpose of recording this enormous progress that I have 

 ventured to assume the office of stock-taker. The year 1851 may be regarded as 

 occurring towards the close of one epoch and the dawn of a new era in cheniical 

 history. Consider broadly the state of organic chemistry at that time. There is 

 no occasion for going into detail, even if time admitted, hecause our literature has 

 recently been enriched by the concise and excellent historical works of Schor- 

 lemmer and of Ernst von Meyer. It will sulhce to mention that the work and 

 writings of Liehig, Berzelius, Wohler, Dumas, Gay-Lussac, Bunsen, and others 

 had given us the leading ideas of isomerism, substitution, compound radicles, and 

 types. Wurtz and Hofmann had just discovered the organic ammonias ; William- 

 son that same year made known his celebrated work on the ethers ; and Gerhardt 

 discovered the acid anhydrides a year later. The newer theory of types was 

 undergoing development by Gerhardt and his followers ; the mature results were 

 published in the fourth volume of the ' Traiti? de Chiniie ' in 1856. In this country 

 the theory was much advanced by the writings of Odling and Williamson. 



Subsequent Development oe Chemistry along Two Lines. 



The new era which was dawning upon us in 1851 was that of structural or 

 constitutional chemistry, based on the doctrine of the valency of the atoms. It is 

 well known that this conception was broached by Frankland in 1852, as the result 

 of his investigations on the organo-metallic compounds. But it was not till 1858 

 that Kekul^, who had previously done much to develop the theory of types, and 

 Couper, almost simultaneously, recognised the quadrivalent character of carbon. 

 To attempt to give anything approaching an adequate notion of the subsequent 

 influence of this idea on the progress of organic chemistry would be tantamount to 

 reviewing the present condition of that subject. I imagine that no conception 

 more proliBc of results has ever been introduced into any department of science. If 

 we glance back along the stream it will he seen that shortly after the last meeting 

 here the course of discovery began to concentrate itself into two channels. In one 

 we now find the results of the confluent labours of those who have regarded our 

 science from its phy.sical side. In the other channel is flowing the tide of discovery 

 arising from the valency doctrine and its extension to the structure of chemical 

 molecules. The two channels are at present fairly parallel and not far apart ; an 

 occasional explorer endeavours now and again to make a cross-cut so as to put the 

 streams into communication. The currents in both are running very rapidly, and 

 the worker who has embarked on one or the other finds himself hurried along at 

 such a pace that there is hardly breathing time to step ashore and see what his 

 neighbours are doing. It speaks well for the fertility of the conception of valency 

 that the current in this channel is flowing with unabated vigour, although its 

 catchment area — to pm-sue the metaphor — is by no means so extensive as that of 

 the neighbouring stream. 



The modem tendency to specialisation, which is a necessity arising from the 

 large number of workers and the rapid multiplication of results, is apparently in 

 the two directions indicated. We have one class of workers dealing with the 

 physics of matter in relation to general chemical properties, and another class of 

 investigators concerning themselves with the special properties of individual com- 

 pounds and classes of compounds — with atomic idiosyncrasies. The workers of 

 one class are diflerentiating while their colleagues are integrating. It would he 

 nothing less than unscientific to institute a comparison between the relative merits 

 of the two methods ; both are necessary for the development of our science. All 

 methods of attacking the unknown are equally welcomed. In some cases physical 

 methods are available, in other cases purely chemical methods have alone been found 

 of use. There is no antagonism, but co-operation. If the results of the two methods 

 are sometimes at variance it is simply because we have not known how to interpret 

 them. The physical chemist has adopted the results of the application of chemical 



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