Physical Constitution of the Sun. 



351 



heat developed in the wire with each value of the light-emission. 

 The rays sent out by the wires were divided into two groups by 

 the employment of a red and a green glass ; and the variations 

 of intensity of each were determined separately. The red glass 

 absorbed all the rays from the violet end of the spectrum to the 

 line D ; while the green glass transmitted these rays, and ab- 

 sorbed those from the red end to the same line. Accordingly, 

 for the intensities employed, the two glasses were nearly comple- 

 mentary, although in different degrees homogeneous. 



On account, however, of the great interest which, as remarked 

 above, is now attached to the knowledge of the relation between 

 the temperature and light-emission of an incandescent body, I 

 thought it would be worth the trouble to examine whether a 

 simple relation subsists between the amounts of light observed 

 by me to be evolved by galvanically incandescent platinum wires 

 and the quantities of heat developed in them. 



I take leave here to communicate first the data of observation 

 taken from Table III. in the memoir mentioned (Pogg. Ann. 

 vol. cix. p. 267), referring to the paper itself for a more precise 

 account of the experiments. 



The fundamental units and their proportion in the quantities 

 of light for red light (J,,) and green light (J x ) are unknown. 

 In the arrangement of the observations the intensity of the gal- 

 vanic current was always so regulated that with the different 

 wires the quantities of light emitted were the same ; the heat 

 developed differed according to the proportion of the different 

 thicknesses of the wires. 



Wire No. I. had a thickness of 0*178 millim.; the other, 

 No. IV., a thickness of O1035 millim. The quantities of heat 

 developed were measured by the product of the resistance into 

 the square of the current-intensity. 





Light. 



Heat. 



No 









J P 



Jx 



Wj 



Wiv 





(Red). 



(Green). 



(Wire I.). 



(Wire IV.). 



1. 



301 



78 



4-494 



5 000 



2. 



670 



174 



5011 



5-387 



3. 



1170 



409 



5-413 



5-948 



4. 



2500 



831 



5-984 



6-345 



5. 



4132 



1611 



6-502 



6947 



6. 



5868 



2450 



6-600 



7-338 



7. 



7500 



3290 



6-768 



7-469 



8. 



8830 



4333 



6-908 



7601 



A glance at these values shows immediately that there is no 

 proportionality between the light evolved and the heat developed 



