on the Temperature of the Sun, 



445 



It 



on. 



Sept. 11 



f Iron bare 



1 



Sept. 12 | 

 Sept. 26 { 



blackened 

 bare . , 

 blackened 

 bare . . 

 blackened 



Div. 

 77-75) 

 87-5 J 

 63-5 1 

 72-75 J 

 116-0 | 

 131-0 J 



Ratio. 



Mean value for emissive power of iron 



Plati 



f Platinum bare 



Sept. 11 

 Sept. 3 

 Sept. 26 

 Sept. 26 



Mean value for emissive power of platinum 



blackened 

 bare . 

 blackened 

 bare . . 

 blackened 

 bare . . 

 blackened 



0- 



0-873. 



0-886. 

 0-882. 



Ratio. 



0*364. 



0-338. 



0-360. 



0*337. 

 0-350. 



Cylinders of Magnesium Oxychloride. — As I proposed to 

 make experiments upon the radiation of small cylinders of 

 magnesium oxychloride when rendered incandescent by the 

 oxyhydrogen flame, I wished to determine also the emissive 

 power of this substance. The cylinders had a diameter of 

 about 6 millims. I placed the one upon which I meant to ex- 

 periment in a horizontal position so that its end penetrated 

 into the Bunsen flame and occupied the same position as the 

 disks in the preceding experiments ; and I obtained the follow- 

 ing results : — 



Sept. 12 | 

 Sept. 3 | 

 Sept, 26 | 



T> 



;? 



V) 



?> 



JJ 



?? 



Div. 



15*5 



26- 



14-8 



25- 



Oxychloride mag. bare . 



blackened, 

 bare . 

 blackened, 

 bare . 

 blackened. 

 Mean value for emissive power of magne- ) 

 sium oxychloride j 



•51 



1-0/ 



:«81 



•5/ 



23-9 1 



41-6 J 



Ratio. 

 0-596. 



0-580. 



0-572. 



0-584. 



Therefore, at high temperatures, the emissive powers of 

 Cu, Fe, Pt, and Mg. oxychloride are represented by the 

 numbers 0'943, 0'882, 0'350, 0-584. 



