400 SCIENTIFIC THOUGHT. 



A great door was now opened, not only for actual 

 observation and research, but also for speculation i.e., 

 for abstract thought. Some substances, if they entered 

 into combination with hydrogen, required more than one 

 unit of hydrogen, and it might therefore be that the pro- 

 portion of the combining weight of hydrogen with any 

 substance did not correctly give the atomic weight of the 

 latter, but merely a multiple or sub-multiple of it. Thus, 

 assuming oxygen combined with hydrogen in the propor- 

 tion of 8 parts of the former to 1 part of the latter, a 

 possibility was that the proportion might more correctly 

 be written 16 to 2 than 8 to 1. Then, again, were the 

 equivalent or atomic weights necessarily whole numbers ? 

 Were combinations all binary, such as acids and alkalies 

 forming salts ? and were more complex compounds resolv- 

 able into binary compounds of simpler binary compounds ? 

 Further, assuming the proportions fixing the combining 

 weights to be known, how did the volumes of bodies com- 

 bine? was there a rule of volumes as there was of weights? 

 and lastly, what was the reason or cause which made sub- 

 stances change their combinations, forming new ones, what 

 did chemical affinity consist in, what did it depend on, 

 how could it be defined and measured ? 



Considering that we have to do with a large number of 

 independent, apparently unchangeable, elements, entering 

 into many thousands of differing compounds, the task of 



of heat. Lavoisier led the way in I purely arithmetical relations, and 



the development of the purely arith- 

 metical department of chemistry, 

 in the exclusive study of which 

 physical chemistry was greatly 

 neglected. Dalton suggested a 

 formula which lent itself admir- 

 ably to the representation of these 



Berzelius elaborated this and in- 

 vented a practical nomenclature. 

 Black and Dalton threw out novel 

 ideas ; Lavoisier and Berzelius ela- 

 borated great systems and created 

 great schools which numbered many 

 converts and industrious workers. 



