ILLUMINATION BY REFLECTED LIGHT. 115 



With this apparatus objects may be viewed on a dark or 

 coloured ground; they may be placed in special holders (dark 

 wells), &c. 



By the Lieberklihn mirror the visible portions of the object are 

 pretty equally illuminated, 1 in contrast to the usual effects of light 

 and shadow produced by ordinary side-light. 



1 We meet here and there with vague ideas as to the action of the different 

 illuminating devices. Many microscopists confine themselves exclusively to 

 what they see, without attempting to explain the production of the effect. 

 From the communication of Abbe, already several times quoted, we find that 

 observers who are capable of passing judgment on this point, on account of 

 their mathematical and philosophical attainments, recognize the accuracy of 

 our exposition. 



