OF SULPHURET OP CARBON. 287 



Angle of the prism, 8*10' 



Angle of refraction, 5° 38 



Refractive power, 1.687 



By considering the bisecting ray, as passing through the green 

 space, and near its confines with the blue, the following mea- 

 sures were obtained : 



Angle of the prism, 8° 10' 



Angle of refraction, 5° 27' 



Refractive power, 1.6632 



As the sulphuret of carbon has nearly the same action upon 

 the red and green rays, as balsam of Tolu, I have no doubt but 

 that the bisecting ray is considerably advanced upon the blue 

 .space, and that the mean index of refraction is nearly 1.680. 



A prism of flint glass, with a refracting angle of 20° 53', 

 corrects the colour produced by a prism of sulphuret of car- 

 bon, having a refracting angle of 8° 10; the light being inci- 

 dent perpendicularly upon the fluid prism. Hence it follows, 

 that the dispersive power of the sulphuret, or the value of 



-n =- is 0.115, R being the index of refraction, and d the part 



of the whole refraction to which the dispersion is equal ; and 

 that the refractive power of the extreme red ray is 1.623, and 

 the refractive power of the extreme blue ray 1.737. 



From these experiments we conclude, that the sulphuret of 

 carbon exceeds all fluid bodies in refractive power, surpassing 

 even flint-glass, topaz and tourmaline ; and that in dispersive 

 power, it exceeds evert/ fluid substance, except oil of cassia, hold- 

 ing an intermediate place between phosphorus and balsam of 

 Tolu. 



These relations will be better understood from the following 

 short Tables : 



O o 2 Refractive 



