SELENITE FILMS. 



241 



the reader will be able to make out its construction from 

 the illustration. 



Mr. Swift's complete condenser, which has been already 

 shown at Fig. 44, is also fitted with selenite discs for colour 



FIG. 210. 



development, and also with a revolving film of mica, by 

 the combinations of which a very great number of tints 

 may be obtained. 



Barker's selenite discs, as made by Messrs. Beck, are 

 shown in Fig. 211, and are very useful, seeing that one or 

 all of them can be put in and out of use in a moment. 



FIG. 2ii. FIG. 212. 



This form has been modified by Mr. Richards, who read a 

 paper upon "A New Method of using Barker's Films" 

 before the Royal Microscopical Society, March 9th, 1870. 



R 



