1884.] 



MICROSCOPICAL JOURNAL. 



79 



It was not necessary for him to ' work 

 it out' at all, although it may have taken 

 considerable of his time to work it out so 

 as to try and introduce, if possible, some 

 variation from my plan as shown him. 

 The parties named by me do not say 

 they never saw any details or saw any 

 drawings. Mr. Pennock writes me that 

 he does not recollect any, but Dr. R. J. 

 Mohr and Mr. Kd. Bausch do recollect 

 the fact of my showing them drawings, 

 and of discussing the merits of the device ; 

 and Mr. Bulloch himself has shown to a 

 certain party, since last September, the 

 drawing 1 made in his own note-book, 

 three years ago, of this very device. 

 Whether it was the drawing I made or 

 not I do not assert. 



But 1 do not wish to pursue this subject 

 any further. If you will kindly publish 

 herewith the drawings sent you some time 

 ago, copied from my original sketches 

 made three years ago, the readers of 

 this magazine will be able to judge for 

 themselves how 'crude' the 'suggestion' 

 was, and how much Mr. Bulloch has 

 ' worked it out.' 



It is to be noted that while Mr. Bulloch 

 says, at the opening of his letter, that he 

 has always given me the credit of sug- 

 gesting the idea, but that he had to work 

 it up into shape, etc., he has never pub- 

 licly made any such statement in any 

 print I have seen, but, on the contrary, 

 has published the device as his own in 

 this Journal, in the journal of the Royal 

 Microscopical Society and elsewhere, 

 without a word or a hint that any one else 

 had suggested it. 



Albert McCalla. 



Fairfield, Iowa, March 3d, 1884. 



[The figures referred to above are given 

 on another page of this number. — Ed.] 



o 



Homogeneous Immersion. 



To THE Editor: I find in the micro- 

 scopical journals nowadays a good deal 

 about homogeneous immersion lenses, 

 but all the articles I have seen assume 

 that the medium used shall have the same 

 refractive index and dispersive power as 

 the front lens of the objective, which is 

 usually of crown-glass of refractive index 

 about 1.525. 



It seems to me to make a lens which 

 shall work through different thicknesses 

 of cover-glass equally well and without 

 adjustment, the immersion medium should 

 correspond with the cover-glass, so that 

 the combined thickness of glass and im- 



mersion fluid would always be the same 

 (although the thickness of each varied) 

 for an object in contact with the under 

 side of the cover. 



The refractive index of cover glass is 

 said to be 1.55, quite a little higher than 

 crown glass, and its dispersive power is 

 probably greater, as it is, or is supposed 

 to be, a light flint glass. 



By making the ifront lens of the same 

 kind of glass (the Tolles 4, owned by Mr. 

 Frank Crisp, the angular aperture of which 

 was calculated by Mr. Keith, has a front 

 of 1.55 index), the light would pass straight 

 from the object to the back surface of the 

 front lens, and would allow lenses of a 

 little greater aperture to be made. 



Louis H. Noe. 



February, 1884. 



Cleaning Slides and Covers. 

 To THE Editor: Regarding G. T.'s 

 inquiry as to how slides and covers are 

 cleaned, I would say that my practice has 

 been to save all my failures until cleaning 

 day, and then place them in turpentine 

 for two or three hours or more, when they 

 are easily cleaned with the fingers. Sub- 

 sequently they are washed in liquor po- 

 tassa and rinsed in soft water. 



Jas. C. Lathrop. 



MICROSCOPICAL SOCIETIES. 



A committee of the New-York Society, 

 appointed at the meeting held December 

 21st, to present in a formal manner the 

 sentiments of the society in view of the 

 death of Mr. Robert B. Tolles, adopted 

 the following remarks, made by Mr. Wil- 

 liam Wales at that meeting, as an appro- 

 priate and satisfactory expression of those 

 sentiments : — 



' The death of Mr. Tolles has been to 

 me a source of deep regret. For modesty, 

 for uprightness, for earnestness of pur- 

 pose he was one of the most estimable of 

 men. A larger capacity than his, a firmer 

 and finer skill, a more artistic feeling, a 

 sterner conscientiousness has seldom, if 

 ever, been devoted to the work of making 

 the microscope a thoroughly efficient and 

 trustworthy aid in scientific researches. 

 The fortunate owner of one of his fine 

 lenses possesses one of the most exquisite 

 pieces of mechanism ever produced by 

 the mind and hand of man. Mr. Tolles 

 loved his beautiful art. He loved it better 

 than riches, for he died a poor man. He 

 loved it better than life, for its pursuit, ne- 



