MI.M.IIK I.] TIIK KAIMATION.s OF IGNITED BOD1IX 33 



lint- I') in tlie reil almost as far as the line F in the green, 

 the colors present being red, orange, and a tint which 

 may be designated as gray. There was nothing answer- 

 ing to yellow. The rays first visible through this ap- 

 paratus may therefore be designated as red and greenish- 

 <rr:iy ; the former commencing at the line B, and the lat- 

 ter continuing to F, as at 3. 



The voltaic current was now increased, and the tem- 

 perature rose to 1325. The red end of the spectrum 

 remained nearly as before, but the more refrangible ex- 

 tremity reached the position of the little fixed line d. 

 Traces of yellow were now visible, and, with a certain 

 degree of distinctness, the red, orange, yellow, green, and 

 a fringe of blue could be seen ; 4 shows the result. 



The temperature was now carried to 1440. The red 

 extremity appeared to be advancing towards the line A ; 

 the blue had undergone a well-marked increase. It 

 reached considerably beyond the line G, as shown at 5. 



On bringing the platinum to 2130, all the colors were 

 present, and exhibited considerable brilliancy. Their ex- 

 tent was somewhat shorter than that of the daylight 

 spectrum, as seen at 6. 



Having thus by repeated experiments ascertained the 

 continued extension of the more refrangible end as the 

 temperature rose, it became necessary to obtain obser- 

 vations for degrees below 1210, the limit of visibility 

 through the telescope. I therefore carried the prism 

 nearer to the platinum, and looking with the unassisted 

 eye directly through it at the refracted image, found that 

 it could be distinctly seen at a temperature as low as 

 1095. Under these circumstances, the total length 

 could not be compared by direct measurement with the 

 other observations, and the result given at 2 is as cor- 

 rect as could be obtained. The colors were red and 

 greenish-gray. 



C 



