1895.] MICROSCOPICAL JOURNAL. 183 



On the Use of Colored Light in Microscopy. 



By ARTHUR M. EDWARDS, M. D. 

 NEWARK, N. J. 



For several years, indeed since 1865, I have felt that 

 it is a fact not sufficiently appreciated by microscopists 

 in general that the clearness with which an object can 

 be seen depends much more upon the character of the 

 illumination than upon the intensity of the light derived 

 therefrom. Color is vastly more important than bril- 

 liancy. It is a common mistake to suppose that if an ex- 

 tremely powerful mode of illuminating the object viewed 

 by means of the microscope be obtained that an improv- 

 ed definition must necessarily result. But the fact is, on 

 the contrary, that a feeble beem, if it be of the proper 

 color, will enable more to be seen than if a bright light 

 of an improper tint be used. In 1871, I had a conversa- 

 tion with Mr. Charles Spencer, the celebrated optician, 

 on the subject when he detailed to me the results he had 

 arrived at during the testing of microscopic lenses and 

 which were confirmatory in a very striking manner of 

 my experiments and the theory I had formed for'myself 

 working independently during the preceeding years. I 

 shall not endeavor to detail all the various experiments 

 I undertood but shall briefly state what led me towards 

 these investigations and the summary of the results I 

 arrived at. 



In the year 1865, I was engaged in experimenting on 

 the obtaining of photographic representatives of micro- 

 scopic objects, more particularly the Bacillariaca?, and 

 this led to my endeavoring to ascertain the best appa- 

 ratus to be made use of in arriving at the desired results. 

 Of the mechanical part of the problem, namely respect- 

 ing the microscope irrespective of the various lenses 

 employed as well as the camera made use of I shall say 



