II. SELECTORS. 213 



843. Mitscherlich's Stand for use in the spectroscopic 

 examination of coloured flames. 



Prof. A. Mitscherlich, Miindtn. 



843a. Direct-vision Spectroscope of gre.it dispersive 

 power, provided with a specially constructed micrometer for mea- 

 suring intervals between lines to '0001 in. A. Hilger. 



843b. Two powerful Direct-vision Spectroscopes, 7 in. 



in length. A. Hilger. 



844. Pocket Spectroscope, showing sodium line in a 

 simple burning candle, of great use in chemical and meteorological 

 observations. A. Hilger. 



845. Hilger's Pocket Spectroscope, showing all the prin- 

 cipal Fraunhofer lines, dividing D easily with nickel line between; 

 when on sun, a sliding slit with division adjustable to position, 

 besides a limb in front of eyepiece. A. Hilger. 



846. Pocket Spectroscope of the simplest and cheapest 

 kind. A. Hilger. 



847. Rhomboid of Iceland Spar. . /. Hilger. 



Iceland Spar Prism of 60, 1-J. in. surfaces, single re- 

 fracting. A. Hilger. 

 Spar Prism, 1| in. surfaces. A. Hilger. 

 Flint Prism, 1 J- in. surfaces. A. Hilger. 

 Flint Prism, 1 in. surface. A. Hilger. 

 Two Half Prisms, 1 in. surface. A. Hilger. 

 Lateral Flint Prism, If in x 3 in. A. Hilger. 



Three compound Direct-vision Prisms, one of a new 



form receiving light at right angles. A. Hilger. 



Four compound Prisms without colour. A. Hilger. 



Two dull Glass Prisms for photometric use. A. Hilger. 



Nicol Prisms for polarisation. A. Hilger. 



Double Image Prism. A. Hilger. 



Parallel Plane Glass Plate, surface 3 in. x 2^ in. 



A. Hilger. 



848. Nicol and a Double Image Prism. A. Hilger. 



848a. Large Prism of 60, with perfectly worked surfaces 

 3 in. bv 3| in. of the finest Thalium glass, on brass stand. 



A. Hilger. 



848b. Two Nicol Prisms mounted for polarisation. 



A. Hilger. 



