ISO SCIENCE PROGRESS 



mination to keep to facts, and facts alone, they attempted to 

 express the facts of combination in formulas, wherein each 

 symbol represented a combining weight of an element, that is, 

 the smallest quantity by weight of it that combines with unit 

 weight of the standard element. But they were soon stopped 

 by the same difficulty which had stopped Dalton. They found it 

 impossible to discover a principle which would enable them to 

 select the value of each combining weight from the many 

 possible values, all of which were in keeping with the facts. 



Some chemists kept the Daltonian language, and spoke of 

 atoms and particles, but could not form a clear, mental picture 

 of either the atom or the particle ; others tried to express all 

 the facts about composition without a theory of the structure 

 of matter, but found themselves in difficulties as great as those 

 which confused and blocked the way of the atomists ; another 

 school thought to escape the stumbling-blocks that tripped up 

 their companions by using the conception of equivalent weights, 

 rather than either combining weights or atomic weights, but 

 could not find a satisfactory working definition of equivalent 

 weight. Chemistry was in confusion. In the midst of the 

 confusion Cannizzaro was born. 



During the years when Cannizzaro was receiving his training 

 in natural science, chemistry was becoming more and more 

 confused. The disorder reached its height in the fifties of last 

 century. There were then many competing systems, each 

 claiming the monopoly of chemical truth, each violently sup- 

 ported by men who as violently condemned all the others. 

 Meanwhile, work in the laboratories went on, facts were gathered 

 in, minor hypotheses were started and tried by their fruits, 

 the science advanced, the times were ripening for the coming of 

 the great interpreter. 



In the year before the birth of Cannizzaro a gaseous com- 

 pound of carbon and hydrogen was isolated by Faraday, and 

 proved by him to have the same composition as olefiant gas, 

 but to differ from that gaseous compound in relative density 

 and other properties. Remarking on the differences which he 

 observed between the interactions of chlorine with olefiant gas 

 and the new compound, Faraday said : 



" This is a remarkable circumstance, and assists in showing 

 that though the elements are the same, and in the same pro- 

 portions as in olefiant gas, they are in a very different state of 



