THE MICROSCOPE. 85 



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Editors of The Microscope : 



In the April issue of this journal appeared a short paragraph 

 stating that I had claimed to have resolved amphipleurci pellucida by 

 central sunlight. 



If my letter to Dr. Stowell was so worded, without qualification, 

 it was a mistake on my part, for I intended to convey the idea of 

 having the mirror central. 



That the light enters the objective very obliquely is easily 

 proved, both by the color of the object and by removing the eye- 

 piece and looking down the body. In fact, it is the light of greater 

 obliquity than 41° in glass (equal to 90" in air, or an aperture of 

 r" N. A.), that really does the work. 



When the light is condensed by the mirror upon the front of 

 the objective, a large amount of it is radiated from the imperfect 

 polish of the front cell. All of this light in excess of 41" from the 

 perpendicular, is totally reflected from the lower surface of the slide. 

 Some of this passes through the object and enters the objective. 



I believe Mr. Ed. Bausch was the first to make use of this 

 method of illumination, since which time it has been done by sev- 

 eral microscopists and with various objectives. Those with which 

 I have succeeded are the new B. &: L. |- and \ of 140", B. A.; Spen- 

 cer's \ of 110°, B. A., and \ of 130 B. A.; and Gundlach's Jg- 105° 

 B. A. That there are many others capable of doing the same I have 

 no doubt. Allen Y. Moore, 



53 Prospect Street, Cleveland, Ohio. 



Elmira, June 10, 1882. 

 My Dear Doctor: — Of course you are coming to Elmira to 

 join the assemblage of Microscopists who mean to journey hither 

 on August 15th. We have received intelligence from most of the 

 prominent members of the American Society of Microscopists, 

 stating their determination to be present, and giving title of papers 

 to be presented upon that occasion. We mean to have a good time, 

 and the Elmira Society are making every preparation for the recep- 

 tion and entertainment of their guests. All members of the Amer- 



