448 Experimental Researches on the 'Temperature of the Sun. 



ployed to heat the cylinder was very short ; but the heat from 

 it was so intense that the platinum flowed like wax. It must 

 be understood that in all these experiments the second reading 

 on the galvanometer was subtracted from the first — the latter 

 representing the effect of the radiation of the cylinder and 

 flame, the former the radiation of the flame and surrounding 

 bodies. It should also be remembered that a double screen 

 with a hole in it a little larger than the base of a cylinder was 

 placed between the latter and the pile, so that the influence of 

 surrounding bodies was very small. The following are the 

 results which were obtained. 



First Series. 



Cylinder of Magnesium oxy chloride bare * diameter 6*1 

 millims. ; surrounding temperature 24°*4 ; distance from the 

 pile 588 millims. 



First experiment. — Deflection of the galvanometer 11*2 di- 

 visions. 



We find by calculation that, if the distance of the pile 

 had been 6*1 4- 107*17 millims. (in order to make the 

 radiating surface appear as if at an angle of 32' 3 //# 6), the 

 reading would have been ^=9-051 divisions. But if we re- 

 member that the emissive power of magnesium oxychloride 

 is 0*584, we find that, if the cylinder had been covered with 

 lampblack (i. e. if its emissive power had been equal to 1), 

 the thermal effect would have been equal to 



y ~ E = (F584 =15 ' 499 divisions. 



Introducing this value of y into the formula, if £ 1 = 24 0, 4 

 we shall have = 297°*4, and we thus obtain T = 2169° and 

 £ = 1896°. 



Second experiment. — Under the same conditions as the first. 

 Deflection 12*3 millims., giving y x = 9*9404 millims., 



By the formula we obtain 



T=2236°, £=1963°. 

 Third experiment. — Heading on galvanometer 12*2 divisions. 

 */ 1 = 9*859, y=16*84, 

 T=2227°*5, *=1954°*5. 



Second Series. 

 First experiment. — The light was dazzling. Distance from 



