ELEMENTARY PHOTO-MICROGRAPHY. 65 



neath the silver coin. The central spot, which 

 gives colour to the background, should be rather 

 darker than the ring outside it. The result of 

 a red ring with a blue centre would be a red object 

 on a blue background. Without doubt the method 

 is well adapted for the study of living organisms 

 and diatom structure as well as for photography. 



Pleasing effects are obtainable by dividing the 

 outer annular ring into quarters, with two opposite 

 sections of one colour top and bottom say red, 

 and the other two (right and left) green with a 

 black spot in the centre. Such a combination 

 would make the texture of silk cloth mounted in 

 Canada balsam appear as if the warp were one 

 colour and the weft -another. 



Mr. Rheinberg recommends blue or green for 

 the central spot rather than red or orange, and 

 says that a green centre with red periphery will 

 give superior results to a red spot and green 

 periphery. 



For resolution of diatom structure a blue 

 periphery and a small clear centre are the most 

 advantageous. 



