Analysis by Spectrum-observations. 



91 



object-glasses of the telescopes B and C is placed a hollow 

 prism, F, filled with bisulphide of carbon, and having a refracting 

 angle of 60°. The prism rests upon a brass plate moveable 

 about a vertical axis. The axis carries on its lower part the 

 mirror G, and above that the arm H, which serves as a handle 



for turning the prism and mirror. A small telescope placed 

 some way off is directed towards the mirror, and through this 

 telescope an image of a horizontal scale, fixed at some distance 

 from the mirror, is observed. By turning the prism round, every 

 colour of the spectrum may be made to move past the vertical 

 wire of the telescope C, and any required position in the spec- 

 trum thus brought to coincide with this vertical line. Each 

 particular portion of the spectrum thus corresponds to a certain 

 point on the scale. If the luminosity of the spectrum is very 

 small, the wire of the telescope C may be illuminated by means 

 of a lens, which throws a portion of the rays from a lamp through 

 a small opening in the side of the tube of the telescope C. 



We have compared the spectra represented on the Plate, which 

 we have obtained from the pure chlorides, with those produced 

 when the bromides, iodides, hydrated oxides, sulphates and 

 carbonates of the several metals are brought into the following 

 flames : — 



Into the flame of sulphur. 



„ „ bisulphide of carbon. 



„ „ aqueous alcohol. 



Into the non-luminous flame of coal-gas. 



Into the flame of carbonic oxide. 

 „ „ hydrogen. 



Into the oxyhydrogen flame. 



As the result of these somewhat lengthy experiments, the 

 details of which we here omit, it appears that the alteration of 



H2 



