concerning Heat. 



As the quantities of light directed toward both were 

 equal, and as the diameters of the spectra, and conse- 

 quently the densities of the light that formed them were 

 also equal, there could be no difference between the re- 

 sults of the experiments with the two reservoirs, except 

 what was occasioned by the difference in the direction of 

 the rays that .formed the spectra. On one hand these 

 rays were convergent, and on the other divergent ; and I 

 had inferred that if parallel rays were in reality less effica- 

 cious in exciting heat than convergent rays, as some 

 philosophers have supposed, divergent rays must be still 

 less efficacious than parallel rays, and consequently much 

 less than convergent rays. 



Having made the experiment with all possible care, 

 I found no sensible difference between the quantities of 

 heat excited in a given time by divergent and convergent 

 rays. 



The following are the particulars of the progress and 

 results of this experiment. 



From the results of all the experiments of which I 

 have just given an account to the Class, we may con- 

 clude that the quantity of heat excited or communi- 

 cated by the solar rays is always, and under all circum- 

 stances, as the quantity of light that disappears. 



[This paper is, in part, printed from Nicholson's Journal, XII. 

 (1805), pp. 65 -75 and 154-171; and in part translated from the 

 Memoires de PInstitut, etc., VI. (1805), pp. 88- 133.] 



