46 BIOGRAPHIES OF SCIENTIFIC MEN 



and criticism, on history and general policy, on civil law, 

 and on anatomy. A goodly number of subjects, but 

 Priestley was a most versatile man, as the catalogue of 

 his 108 books published in 1794 bears witness. During 

 his six years' residence at Warrington, he married the 

 daughter of Isaac Wilkinson, an ironmaster of Wrexham, 

 and the union proved a happy one. In 1766 he became 

 acquainted with Benjamin Franklin 1 (who lived in Craven 

 Street, Strand, London). The acquaintance ripened into 

 friendship. Franklin encouraged Priestley in his philoso- 

 phical pursuits, and no doubt this was the origin of his 

 electrical researches, which were subsequently published 

 in his History of Electricity. This work greatly enhanced 

 his fame, and gained for him an F.R.S., and the degree 

 of LL.D. of Edinburgh University. 



In 1767 Priestley left Warrington for Leeds, having 

 been appointed minister of Millhill Chapel. In the York- 

 shire town he commenced his chemical investigations, 

 at the same time freely expressing his opinions on theology 

 and metaphysics. Living near a brewery, he made experi- 

 ments on the " fixed air " (carbon dioxide) of Black, and 

 this led to investigations with " airs," or, as we should 

 say, with gases. Priestley's chemical work was essentially 

 in the domain of pneumatic chemistry. In 1772 he 

 published a work on the method of impregnating water 

 with fixed air hence the birth of the mineral water 

 1 Born 1706; died 1790. 



