Manchester Memoirs, Vol. xlvii. (1903), No. 11. 23 



conclusions. For instance, chlorine, bromine, iodine, 

 nitrogen, and phosphorus become compounds of hydrogen 

 with as many unknown or " ideal " elements, which no 

 actual analysis has yet identified. That is, the known 

 phenomena of chemistry seem to be less simply interpreted 

 by Brodie's calculus than in our commonly accepted 

 theories, and certain classes of phenomena are not con- 

 sidered at all. It is true that Brodie never completed his 

 work, but it is not easy to see how his notation and 

 reasoning could have accounted for isomerism, much less 

 for the facts which stereochemistry seeks to explain. 



Just here we find the prime difficulty of all attempts 

 to evade the atomic theory. Up to a certain point we 

 can easily dispense with it, for we can start with the fact 

 that every clement has a definite combining number, and 

 then, without any assumptions as to the ultimate meaning 

 of these constants, we can show that other constants are 

 intimately connected with them. So far, we can ignore 

 the origin of the so-called atomic weight; but the moment 

 we encounter the facts of isomerism or chemical structure, 

 and of the partial substitution of one element by another, 

 our troubles begin. The atomic theory connects all of 

 these data together, and gives the mind a simple reason 

 for the relations which are observed. We cannot be 

 satisfied with mere equations ; our thoughts will seek for 

 that which lies behind them ; and so the anti-theorist fails 

 to accomplish his purpose because he leaves the human 

 mind out of account. The reasoning instrument has its 

 own laws and requirements, and they, as well as the 

 empirical observations of science, must be satisfied. Even 

 in astronom)' the law of gravitation is not enough ; men 

 are continually striving to ascertain its cause ; and no 

 number of failures can prevent them from trying again and 

 yet again to penetrate into the heart of the mystery. In 



