74 PRIESTLEY. 



losophy ;' * Doctrine of Necessity ;' * On the Roman 

 Catholic Claims ;' ' On the French Revolution ;' ' On 

 the American War ;' beside twenty volumes of tracts 

 in favour of the Dissenters and their rights. His gene- 

 ral works fill twenty-five volumes,* of which only five 

 or six are on scientific subjects : his publications being 

 in all one hundred and forty-one (in one year ten), of 

 which only seventeen are on scientific matters. He 

 is one of the most voluminous writers of any age or 

 country, and probably he is of all voluminous writers 

 the one who has the fewest readers. This arises from 

 the circumstance that, though his political opinions are 

 shared by many, the bulk of his works are theological 

 and metaphysical, but especially theological ; and his 

 religious opinions were confined to an extremely small 

 class of persons. Indeed it may be questioned if he 

 was not in several respects the only person who held 

 his peculiar faith upon all points. 



It happened, fortunately, that when he went to 

 reside at Leeds in care of the Mill-Hill chapel, his 

 house immediately adjoined a common brewery, and 

 this led him to make experiments upon the fixed air 

 copiously produced during the process of fermentation. 

 It must be observed, that long before this time the 

 great step had been made by Black of ascertaining 

 that there are other permanently elastic fluids than our 

 atmosphere, and which have properties wholly different 

 from it. Cavendish, too, had very recently subjected 

 both fixed and inflammable airs (carbonic acid and 

 hydrogen gases) to accurate experiments, showing 

 their relative specific gravities, and proving that they 

 were of the same nature from what bodies soever they 

 were obtained. The probability was, that other 

 gaseous fluids existed in nature as well as those two 

 and common air. The experimenter had, therefore, 

 thenceforth, his attention directed to meeting with 



* Edited by the affectionate care of an able and worthy man, Mr. 

 Towell Eutt. 



