SPECTEO-MICROSCOPY. 123 



without any preparation ; and, when desirable, the same 

 prism can be placed below the stage, and a micrometer 

 used in the eye-piece of the microscope, thus avoiding a 

 multiplication of apparatus. 



The latest improvement is that shown in fig. 75, also 

 effected, by Mr. Browning, who deserves great credit for 

 the skill displayed in the invention and construction of 

 this new and elegant micro-spectroscope. 



Fig. 75. The Sorby-Browning Micro-spectroscope. 



The prism is contained in a small tube, which can be 

 removed at pleasure. Below the prism is an achromatic 

 eye-piece, having an adjustable slit between the two 

 lenses, the upper lens being furnished with a screw 

 motion to focus the slit. A side slit, capable of adjust- 

 ment, admits, when required, a second beam of light from 

 any object whose spectrum it is desired to compare with 

 that of the object placed on the stage of the microscope. 

 This second beam of light strikes against a very small 

 prism, suitably placed inside the apparatus, and is reflected 

 up through the compound prism, forming a spectrum in 

 the same field with that obtained from the object on the 

 stage. 



A is a brass tube, carrying the compound direct vision 

 prism. B, a milled head, with screw motion to adjust the 

 focus of the achromatic eye lens, c, milled head, with 

 screw motion to open or shut the slit vertically. Another 



