1892.] MICKOSCOPICAL JOURNAL. ^ 103 



Sewage. — Sir Henry Roscoe has isolated i3 organisms from 

 ordinary sewage. The relative power of the different organisms 

 for determining the oxi<lation of organic matter was studied. 

 Proteus vulgaris alone absorbed oxygen energetically. The 

 Trans. Royal Society contains full details and photographs of the 

 organisms. 



MICROS! OPICAL NEWS. 



Death of L. D. Mcintosh. — It is with deep sorrow that we 

 haye to announce the death of L. D. Mcintosh, M. I)., D. D. vS., 

 Vice-President of the Mcintosh Battery & Optical Company, 

 which occurred very suddenly on Tuesday, March i, at De 

 Funiak Springs, Florida, where he had gone to lecture before the 

 Florida Chautauqua on Microscopy and kindred subjects. . 



^A/^hite's Objects. — We have just received a fresh invoice 

 from Europe containing nearly every number in the list. 



CORRESPONDENCE. 



Spencer & Smith's Aplanatic Eye-Piece. — 1 have recently 

 purchased from Spencer & Smith, of Buffalo, N. Y., a i-inch 

 positive eye-piece, which is so far superior to anything I have ever 

 before used (and I have a large assortment) that I feel justified in 

 calling the attention of microscopists to it. In common, I sup- 

 pose, with a majority of workers, I, for a long period, paid no 

 special attention to my eye-pieces, which, however, happened to 

 be good ones, but centered my attention upon the objective and 

 stand. I have long supposed that no available use could be made 

 of any eye-piece for micrometric purposes except in a limited jDor- 

 tionof the centre of the field, never exceeding one-half thereof. 



With the eye-piece in question I find sensibly equal amplifica- 

 tion and no distortion almost to the extreme edge of the field. In 

 this respect it far surpasses the Ramsden and Huyghenian eye- 

 pieces. 



I find also that with it the definition, which I always test on a 

 podura, is much improved, and that it is good almost to the ex- 

 treme edge of the field, and this without any new adjustment of 

 the focus. Altogether this eye-piece, which for want of a better 

 name I shall call '• Spencer & Smith's Aplanatic Eye-piece," is, 

 in my judgment, a distinct advance over existing eye-pieces. I 

 have ordered another one for my Zentmayer filar micrometer, and 

 propose to use it hereafter in my micrometrical work in prefer- 

 ence to those heretofore used. — M. D. Ewell. 



Chicago, March 30, 1892. 



