ELEMENTARY PHOTO-MICROGRAPHY. 8 1 



COLOUR PHOTOGRAPHY (AUTOCHROME PROCESS). 



The colour effects shown by the polariscope 

 may be easily reproduced on Autochrome plates. 

 For this purpose the special filter screen supplied 

 by the Lumiere Co. should be attached to the 

 inside of camera, and the focussing screen be 

 reversed that is, placed with the rough side 

 outwards. 



The Autochrome plate is put into the dark 

 slide with the emulsion surface inwards, so that 

 the glass side faces the microscope. 



With incandescent gas and 3in. objective, an 

 exposure of from one to one and a half hours will 

 be necessary. Subsequent operations are as follow : 



Develop with metoquinone for two and a half 

 minutes, and then wash. Reverse the image with 

 a solution made up just before use as under : 

 Potassium permanganate . 2 grains 

 Sulphuric acid . . . . ^ dram 

 Water . . . . . . 2 ounces 



After covering the plate with this solution, 

 bring the dish out into full light, and allow it to 

 remain three or four minutes, rocking the dish 

 frequently meanwhile. 



Wash for half a minute. 



Now redevelop with the original developer till 

 the plate goes black, which usually takes about 

 three minutes. Wash again for three minutes, 

 and put out to dry. 



