VISIT TO EUROPE: RESIDENCE IN LONDON. 139 



travels published in 1810, Vol. I. p. 70 ; also Vol. I. pp. 17 

 and 20 of the visit to Europe in 1851.) My relations with 

 him were most agreeable and useful to me, but had no 

 particular reference to science. He was, however, ever 

 ready to serve me, and did, many years after, perform an 

 important service in the line of my studies, by sending me 

 large specimen slates from the sandstone quarry of Storeton, 

 near Liverpool, containing fine copies, in relief, of the feet 

 of the Chirotheriurn ; they are now in the Cabinet of Yale 

 College. 



Two gentlemen eminent in science, resided at Manches- 

 ter. I sought them under the guidance of Mr. Taylor, but 

 did not find Dr. William Henry, an eminent author on 

 chemistry, of whose excellent "Elements" I published, a few 

 years after, three American editions with notes. I sus- 

 tained an occasional correspondence with him, and sent 

 him a rather copious table of errata in his work, which he 

 received courteously and even gratefully. 



I found Mr. Dal ton, who was a Quaker, with the plain 

 dress and address of his sect. He was apparently from 

 thirty-five to forty years old. I attended an evening lecture 

 by him on Electricity. The audience was popular, and ladies 

 formed a part of it. The lecture was beautifully illustrated 

 by experiments, and among them, in a darkened room, the 

 electrical discharge was conveyed around the cornices of 

 the room by means of an interrupted wire, cut at short 

 intervals ; and as the discharge passed, there was a brilliant 

 light at each interruption, and without any appreciable suc- 

 cession in time. Mr. Dalton had already distinguished 

 himself by his researches on heat and vapor and evapo- 

 ration and the law of diffusion of mixed gases. His great 

 achievement, however, was the establishment of the doc- 

 trine of definite or equivalent proportions, including the 

 volumes of gases. Gay Lussac in Paris had also brought 

 forward similar views and proofs, before there was any 

 communication between them, or knowledge of each other's 



