28 DALTON'5 INFLUENCE ON JOULE'S WORK. 



opportunity afforded by Dalton's laboratory of becoming 

 intimate with the simple but effective home-made apparatus 

 by which Dalton had accomplished his great work, could 

 not but encourage young Joule in that path of self- 

 dependence in his experimental work, which is a most 

 remarkable feature of his career, and which contributed so 

 greatly to his success. There can be no doubt, however, that 

 Joule possessed constructive genius and powers of mani- 

 pulation far beyond those of his master, whose genius lay 

 rather in the observation of nature and philosophical 

 reasoning. 



It would be perhaps going too far to infer that Joule 

 unconsciously took the leading idea which guided him to 

 his discoveries from Dalton or his work, but it is neverthe- 

 less remarkable that the chief distinction between the 

 experimental work of these men, each in his own line, 

 and that of their early contemporaries, was the same, 

 namely, the substitution of quantitative measurement for 

 mere phenomenal experiments. Dalton determined the 

 chemical equivalents by weighing and comparing the 

 weights to the equivalent weight of hydrogen, thus dis- 

 covering the Atomic Theory and introducing quantitative 

 analysis into chemistry. While Joule, by measuring the 

 several physical and mechanical effects by definite standards. 

 and comparing each with the equivalent electrical effect, 

 arrived at their general equivalence and the law of the 

 universal conservation of energy. 



The young Joules continued to visit Dalton after his 

 illness. He was pleased to see them as well as by the 

 occasional information which they gave him. as resulting 

 from their own observation ; e.g.. from their father's house 

 at Broom Hill they could see as far as Runcorn, and on one 



