PLATS XLII. 



. Sn . 



' 1 crvst.-ils 



Fig. 



Crystal ft' i 

 quartz of granite, 

 with a fluid 

 cavity, p. 



. 266. 



''.\c reflector of Mr. Beck, with. Mr. Sorby's flat mirror, M p. 182. 



Fig. 237- 



a 1 



, reflector. Kg. 266. and Mr Sorby's 

 of the parabolic reflector at. wbieh 



eceived and from -which it is reflected upon the object ; g, flat mirror which reflects the light perpendicularly 

 upon the object from which it returns to a point within the aperture of the object gl-- 



jlass. p. 182. 



Fig. 263. 



Leeson'a eye. piece goniometer for measuring the angles of crystals, p 183. 



Fig. 269. 



Fig. 270. 



Crystals of cholesterine. consisting of exceeding!- 

 crystals, some lying perfectly Mat. x ' p. 183. 



-'rystals of chloride of sodium, or common salt, in 

 the form of cubes. X 130. p. 183. 



[To face page 182. 



