396 Addresses delivered at the Commemoration 



it is to wade through such an elaborate and abstract work; but 

 Dr. Priestley applied himself to the task, learned the art, and applied 

 it successfully ; and, what is more, gave to the world the clearest 

 treatise on perspective which has been seen to this day. It contains 

 not only a perspicuous account of all that was known up to that time 

 on the subject, but he actually gives a new method of delineating 

 any object correctly with common instruments, and fully describes it 

 in a few pages, so that no man can misunderstand it. 



Dr. Priestley's attention to the useful application of knowledge 

 may be traced in other instances. At Birmingham a process of gild- 

 ing buttons was common which was exceedingly destructive to the 

 health of the workmen; the process of amalgamation was gone 

 through over a common fire ; the atmosphere was thereby impreg- 

 nated with mercurial fumes, and the consequence was that the lives 

 of the people were shortened. Dr. Priestley saw at once that this 

 might be altered, and invented a most simple plan for the purpose, 

 by which not only the health of the workmen was ensured, but the 

 quicksilver might be saved, and thus a great ceconomy introduced in- 

 to the manufacture. I saw an apparatus of this description which was 

 erected under the direction of Dr. Priestley himself, and so completely 

 has it answered, that the manufacturers have generally adopted it. 



There was another instance in which he regarded the useful ap- 

 plication of scientific discovery. He discovered that water might be 

 artificially impregnated with carbonic acid gas. He thought this 

 might probably be beneficial, particularly in long voyages, as a re- 

 medy for the sea-scurvy, a disease then much felt. He instantly 

 stated his views to the Lords of the Admiralty ; they referred him to 

 the College of Physicians, who gave attention to the subject, and 

 encouraged Dr. Priestley to proceed, to determine the best process 

 for the purpose. The result was highly favourable ; and then, as 

 was his uniform practice, he communicated to the world all he knew. 

 He therefore published, in a shilling pamphlet, the result of his ex- 

 periments and discoveries in fixed air, and described the mode in 

 which it might be thus employed. 



In his preface to this little book, he says, " If this discovery (though 

 it doth not deserve that name,) be of any use to my countrymen and 

 to mankind at large, I shall have my reward. For this purpose I 

 have made the communication as early as I conveniently could since 

 the latest improvements I have made in the process, and I cannot 

 help expressing my wishes that all persons who discover anything 

 that promises to be generally useful would adopt the same method." 

 He does not arrogate any merit to himself for this discovery ; he at- 

 tributes to Dr. Black the investigation of substances containing fixed 

 air ; to Sir John Pr ingle the observation that putrefaction was checked 

 by fermentation ; to Dr. Macbride the discovery that the effect thus 

 produced was by the fixed air generated in the process : he attributes 

 to Dr. Brownrigg the discovery that Pyrmont and other mineral 

 waters contain this air ; and to Dr. Percival some experiments on its 

 medical uses. There is nothing that is contained in Dr. Priestley's 

 book which he claims as a discovery, except that, by accident, he 



