444 Prof. F. Rosetti's Experimental Researches 



and in the other covered with lampblack, it is evident that we 

 thus have the means of obtaining the emissive power of the 

 body under experiment compared with that of lampblack. The 

 body must be placed exactly in the part of the flame men- 

 tioned ; otherwise the lampblack will rapidly oxidize and expose 

 the metallic surface (see fig. 2). 



I made the bodies upon which I experimented into disks of 

 10 millims. diameter. They were kept in the centre of the 

 flame by a wire or rod of the same substance held in a porce- 

 lain tube. 



The results obtained for some of the bodies were as fol- 

 lows: — 



Copper 



f Disk bare . . 



Dec. 6 

 Dec. 6 

 Dec. 6 



i 

 { 



Sept. 12 | 



Sept. 1 



Mean value for the emissive 

 bare copper in the flame 



blackened 

 bare . . 

 blackened 

 bare . . 

 blackened 

 bare . . 

 blackened 



Div. 



105-9 



113- 



106-3 



114-8 



114-4 



121' 



58-5 



62- 



)ower of 



} 



S3} 



} 



Ratio. 

 0-950. 



0-929. 



0-939. 



0-945. 

 0-956. 



0-943. 



