304 



The Spectroscope and the Microscope. 



D D, an apparatus for holding small tube, that the spectrum 

 given by its contents may be compared with that from any 

 other object on the stage. 



E, square-headed screw, opening and shutting a slit to 

 admit the quantity of light required to form the second spec- 

 trum. Light entering the round hole near E, strikes against 

 the right-angled prism which we have mentioned as being 

 placed inside the apparatus, and is reflected up through the 

 slit belonging to the compound prism. If any incandescent 

 object is placed in a suitable position with reference to the 

 round hole, its spectrum will be obtained, and will be seen on 

 looking through it. 



E shows the position of the field lens of the eye-piece. 



G is a tube made to fit the microscope to which the instru- 

 ment is applied. To use this instrument insert G, like an 

 eye-piece, in the microscope tube, taking care that the slit at 

 the top of the eye-piece is in the same direction as the slit 

 below the prism. Screw on to the microscope the object-glass 

 required, and place the object whose spectrum is to be viewed 

 on the stage. Illuminate with stage mirror if transparent, 

 with mirror and lieberkuhn and dark well if opaque, or by side 



