on the Temperature of the Sun. 



331 



experiments, and also by those of Tyndall on the emission of 

 heat (see Pogg. Ann. vol. cxxiv ; also Wiillner, Lehrbuch 

 der Physik, vol. iii. pp. 215, 216). The best experiments of 

 Melloni and Tyndall have shown that, as the temperature rises, 

 the radiation of the body increases, because not only does the 

 energy of the rays belonging to the primary undulations in- 

 crease, but also new undulations of higher refrangibility are 

 added to them. Thus the effect of radiation increases on 

 account of the very large number of rays of different refran- 

 gibility, and on account of the intensity of each ray. 



In order to ascertain whether the formula properly repre- 

 sents the phenomenon of radiation between the limits of my 

 experiments, and to find out whether it is capable of further 

 extension, I began by determining the value of the constants 

 a and b by means of the experimental data of the preceding 

 Table. By taking experiments 7 and 10, in the first of which 



y = 116'7, T=196'6 + 273=469-6, T-0=172-8, 

 and in the second 



y =204-0, T=256-6 + 273 = 529-6, T-0 = 232-8, 

 I obtained the values 



a = 0'00000335131, 

 5=0-0636833. 



loga=4-5252152-10, 



log 5 = 8-8040253-10, 



In order to make sure whether the formula, with the values 

 of a and b calculated in this way, represents the radiation for 

 all differences of temperature between 0° and 273°, the values 

 of y for intervals of 50° were calculated and compared with 

 the corresponding values taken on the curve. 



Table II. 



Differences 

 of tempe- 

 rature. 

 T-0. 



Temperature 

 observed on 



Absolute 



Ordinates y 



Ordinates y 





the thermo- 



tempera- 

 ture. 

 T. 



taken from 



calculated by 



Difference. 



meter, O. 

 t. 



the curve. 



the iormula. 





o 

 



23-8 



296-8 











50 



73-8 



3468 



172 



16-97 



40-23 



100 



123-8 



3968 



46-4 



46-40 



000 



150 



173-8 



446-8 



90-1 



90-80 



-0-70 



200 



223-8 



496-8 



151-7 



152-69 



-0-99 



250 



273-8 



546-8 



234-7 



234-58 



+012 



272-8 



296-6 



5968 



279-6 



27925 



+0-35 



I wished to determine to what extent the formula of Dulong 

 and Petit was capable of representing the effect of radiation 



