A HISTORY OF SCIENCE 



having the same number of atoms to the molecule are 

 disposed to form the same angles of crystallization a 

 property which he called isomorphism. 



Here, then, were two utterly novel and independent 

 sets of empirical facts which harmonize strangely with 

 the supposition that substances are composed of chem- 

 ical atoms of a determinate weight. This surely could 

 not be coincidence it tells of law. And so as soon as 

 the claims of Dulong and Petit and of Mitscherlich had 

 been substantiated by other observers, the laws of the 

 specific heat of atoms, and of isomorphism, took their 

 place as new levers of chemical science. With the aid 

 of these new tools an impregnable breastwork of facts 

 was soon piled about the atomic theory. And John 

 Dal ton, the author of that theory, plain, provincial 

 Quaker, working on to the end in semi-retirement, be- 

 came known to all the world and for all time as a mas- 

 ter of masters. 



HUMPHRY DAVY AND ELECTRO-CHEMISTRY 



During those early years of the nineteenth century, 

 when Dalton was grinding away at chemical fact and 

 theory in his obscure Manchester laboratory, another 

 Englishman held the attention of the chemical world 

 with a series of the most brilliant and widely heralded 

 researches. This was Humphry Davy, a young man 

 who had come to London in 1801, at the instance of 

 Count Rumford, to assume the chair of chemical phi- 

 losophy in the Royal Institution, which the famous 

 American had just founded. 



Here, under Davy's direction, the largest voltaic bat- 

 tery yet constructed had been put in operation, and 



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