290 HISTORY OF CHEMISTRY. 



of what he had done; and, in 1820, two medals for the encourage- 

 ment of science having been placed at the disposal of the Royal 

 Society by the King of England, one of them was assigned to 

 Dalton, "for his development of the atomic theory." In 1833, at 

 the meeting of the British Association for the Advancement of 



o 



Science, which was held in Cambridge, it was announced that the 

 King had bestowed upon him a pension of 150^.; at the preceding 

 meeting at Oxford, that university had conferred upon him the degree 

 of Doctor of Laws, a step the more remarkable, since he belonged to 

 the sect of Quakers. At all the meetings of the British Association 

 he has been present, and has always been surrounded by the reverence 

 and admiration of all who feel any sympathy with the progress of 

 science. May he long remain among us thus to remind us of the vast 

 advance which Chemistry owes to him ! 



[2nd Ed.] [Soon after I wrote these expressions of hope, the period 

 of Dalton's sojourn among us terminated. He died on the 27th of 

 July, 1844, aged 78. 



His fellow-townsmen, the inhabitants of Manchester, who had so 

 long taken a pride in his residence among them, soon after his death 

 came to a determination to perpetuate his memory by establishing in 

 his honor a Professor of Chemistry at Manchester.] 



Sect. 3. The Theory of Volumes. Gay-Lussac. 



THE atomic theory, at the very epoch of its introduction into France, 

 received a modification in virtue of a curious discovery then made. 

 Soon after the publication of Dalton's system, Gay-Lussac and Hum- 

 boldt found a rule for the combination of substances, which includes 

 that of Dalton as far as it goes, but extends to combinations of gases 

 only. This law is the theory of volumes ; namely, that gases unite 

 together by volume in very simple and definite proportions. Thus 

 water is composed exactly of 100 measures of oxygen and 200 measures 

 of hydrogen. And since these simple ratios 1 and 1, 1 and 2, 1 and 3, 

 alone prevail in such combinations, it may easily be shown that laws 

 like Dalton's law of multiple proportions, must obtain in such cases as 

 he considered. 



[2nd Ed.] [M. Schroder, of Mannheim, has endeavored to extend to 

 solids a law in some degree resembling Gay-Lussac's law of the volumes 

 of gase*. According to him, the volumes of the chemical equivalents 



