The Spectroscope. 



Before entering upon any exposition of the Solar sy- 

 stem, I consider it indispensable to acquaint the reader 

 with the spectroscope, and the researches which have 

 become possible by its aid. 



The Spectroscope. 



This Instrument was invented at the beginning of the 

 last century. Its form is the following. In a rounded 

 barrel-chamber closed on all sides are set six prisms, 



