50 HEATS OF COMBUSTION AND ELECTROLYSIS. 



public) strongly confirm this view, and the quantity of heat 

 which Crawford produced by exploding a mixture of 

 hydrogen and oxygen, may be considered as almost de- 

 cisive of the question. In his unexceptionable experiments 

 one grain of hydrogen produced heat sufficient to raise lib. 

 of water 9*6 degrees." " Now we know from experiment 5. 

 that the heat generated in one of Mr. Groves' pairs by the 



Electrolysis of an equivalent or 32 grains of zinc 



when reduced to the capacity of lib. of water is 9/ -9. 



But from the table of intensities of voltaic arrangements, 

 the intensity of Mr. Groves' pair, compared with the affinity 

 of hydrogen for oxygen, is as 1 to 0*93, whence we have 

 9°*9XO'93 = 9 '2, the heat which should be generated by- 

 combustion of one grain of hydrogen, according to the 

 doctrine of resistances." 



Had this paper been published in 1840, with the 

 guarantee of the Royal Society, it is impossible to doubt 

 that it would have caught the attention of some of the 

 numerous philosophers who were at the time studying these 

 subjects. And had the facts it reveals become generally 

 known at that time, the effect on the course of Joule's 

 subsequent discoveries would in all probability have been 

 great. The revelations that the heat developed by the union 

 of two chemical elements effected in the battery is the 

 same as that developed by combustion, and that the heat 

 has a definite equivalent in the electromotive force between 

 these elements, are so pregnant with suggestions, that 

 had others entered this field of enquiry, Joule's attention 

 might well have been diverted from the line it subsequently 

 followed, and the completion of his work taken out of his 

 hands. As it was, however, Joule was left to follow out his 

 work as his own curiositv led him. 



