130 ON THE EXPANSION OF ELASTIC FLUIDS. 



apparatus, in prefence of Mr. Davy, with the moft complete 

 fuccefs; the fun's altitude being greater, the effeft of his 

 rays was fo great as to raife the thermometer in the invifible 

 ray to 98°, while the vifible red never railed it above 87°. 

 At the fuggeftion of Mr. Davy, we tried feveral experiments 

 with refpeft to the power of the feveral coloured rays in ren- 

 The blue rays il- dering Canton's phofphorus luminous ; and we found, with- 

 luminate Can- out a poffibility of doubt, that the blue rays poffefied that 



ton s phofphorus ...... 



morethan the red power in a much higher degree than the red. There was 

 great reafon to fufpecl: that this power, like that of blackening 

 the nitrate of filver, extended beyond the vifible blue ray . 

 but our apparatus was not prepared for the more delicate part 

 of thefe experiments, which are only mentioned with a view 

 of exciting further refearches on this very interefting fubjecl:, 

 and of giving to Mr. Davy the credit due to him for having 

 firll: thought of the experiment. 



XI. 



On the Expanfion of the Elajlic Fluids by Heat. * By Mr. John 

 Dalton. 



Occafion of the JL HE principal occafion of this effay is another on the fame 

 Experiments and fub j ea hy Meffi . s# de Morveau and du Vernois in the firft 

 vol. of the Annales de Chimie. It appearing to them that 

 the refults of the experiments of De Luc, Col. Roi, de Sauf- 

 fure, Prieflley, Vandermonde, Berthollet and Monge did not 

 fufficiently accord with each other ; and that it would be of 

 importance to determine not only the whole expanfion of 

 each gas from two diftant points, fuch as the freezing and 

 boiling, but likewife whether that expanfion be uniform in 

 every part of the fcale, they inltiluted a Cet of experiments 

 Experiments of exprefsly for thofe purpofes. The refult of which was, that 

 VernoL^ ° U betwixt the temperatures of 32° and 212°, the whole expan- 

 fion of one gas differs much from that of another, it being in 

 one inftance about T \ of the original, and in others more than 

 12 times that expanfion ; and that the expanfion is much more 

 for a given number of degrees in the higher than in the lower 



• Manchefter Memoirs, V. 595. 



