20o THE MICROSCOPE. 



ligible, I have to mention I proposed to Mr. Tolles that he should 

 make a little ring-shaped lens fitting with its upper surface to the 

 lower surface of the objective, encircling the setting of the front 

 lens, and presenting in its outer edge the proper curve which would 

 reflect the light coming from below very obliquely from above on 

 the object in focus, and suggested that such a lens," if mounted in a 

 brass, etc., frame, would probably very much facilitate the resolu- 

 tion. The latter indeed is most beautifully effected in the way de- 

 scribed by any homogeneous, or even glycerine immersion objective 

 that will at all show the lines of amphipleura by lamplight with 

 Woodward prism or hemispherical lens, even if only after con- 

 siderable waxing, provided the sunlight is reflected from the mirror 

 in such a way as to strike the external convex (internally concave) 

 surface of the outer edge of the immersion fluid, unless the latter is 

 used too copiously, or smeared all over the covers. 



Mr. Editor, I send you the above communication which is an 

 extract of an explanation given at a meeting of our State Micro- 

 scopical Society, at the express desire of some of my friends and 

 members of the society. 



Very respectfully, 



H. J. Detmers. 



[The engraving for this article was not completed in time. Ed.] 



Boston, March 19, 1883. 

 My Dear Sir: 



Enclosed please find letter sent for your perusal. I thought it 

 might prove of some interest to you, and have borrowed it accord- 

 ingly. 



I don't think the position tenable, your explanation is no doubt 

 correct. 



Prof. Moore subsequently, in August, remarks that with the 



beam of light below the slide circumscribed to the glass of front 



opening the feat is impossible. 



Yours very truly, 



R. B. Tolles. 



Cleveland, O., May 13, 1682. 

 Dear Stodder: 



* * * I have succeeded in resolving balsamed amphipleura 



petlucida by sunlight from central mirror with the following objectives: 



