•xxxiv Annual Report of the Council. 



'fallen. It was attended by some one hundred and forty men of 

 science, including Liebig, Wohler, Kekule, Kopp, Bunsen, 

 Odling, Roscoe, Dumas, Wurtz, and Cannizzaro. 



The pessimism of the opening speakers gave Cannizzaro his 

 ■opportunity. When Dumas declared that organic and inorganic 

 chemistry were two distinct sciences, Cannizzaro was able to 

 maintain the unity of the science, for he showed that both inor- 

 ganic and organic chemistry ought to be submitted to Avogadro's 

 hypothesis as a controlling principle. Kekule made the declara- 

 tion that the physical molecule and the chemical were not always 

 identical, and that purely chemical researches could be carried 

 on independently of physical considerations. In reply, Canniz- 

 zaro expressed his opinion that the physical and chemical 

 molecules were absolutely identical, and he showed that the best 

 way of establishing the molecular weight of a substance was by 

 means of its vapour density. The hour and the man had come. 

 Cannizzaro's two speeches constituted him the leader of the 

 Conference. His suggestions, immensely aided by the dramatic 

 circumstances in which they were made, were adopted by many 

 of his hearers. His system of chemical formulae and atomic 

 weights, the one still in use, rapidly supplanted the old systems. 

 And not only was the change good in itself, by reason of the 

 clearness which it introduced into chemistry, but it led to 

 unexpected advantages. It led to the establishment of three 

 great doctrines. In the first place, the doctrine of gaseous 

 dissociation was a natural outcome of Cannizzaro's teaching. 

 In the next place, with regard to the doctrine of Valency, 

 Frankland declared that till the atomic weights were placed on 

 " their present consiscent basis, the satisfactory development of 

 the doctrine was impossible." Lastly, the periodic classification 

 of the elements, in the judgment of Newlands and of Mendeleeff, 

 could not have been worked out under any other system than 

 that of Cannizzaro. 



One is glad tg think that the priceless service which 

 Cannizzaro thus rendered lo chemistry was widely recognised. 



