320 THE AMERICAN MONTHLY [Nov., 



MICROSCOPICAL APPARATUS. 



The One-Seventy-Fifth Objective. — Dr. Cutter, who is the 

 Proft ssor of Clinical Morphology and Applied Medicine in the 

 College of Physicians and Surgeons at Boston, has s^nt us some 

 photographs of objects taken with the l-75th which we hope to 

 publish soon. In order to use this objective, a cover-glass is re. 

 placed with a strip of mica only one-two-thousandth of an inch 

 in thickness. Dr. Cutter has practiced medicine 43 years, and 

 has use a microscope nearly all of this time. 



The Griffith Microscope. — A substantial recognition for 

 this queen of grace and utility amongst microscopes has been be- 

 stowed on its owner, Mr. E H. Griffith, in one of the most com- 

 plimentary awards given at the World's Fair. Mr. Griffith's 

 exhibit in the north gallery of the Liberal Arts Building, in the 

 space reserved for the Chicago Academy of S'ience, h s been a 

 center of interest for lay as well as professional visitors at the 

 Fair. 



Rapid Polorization. — Mr. Hans M. Wilder of Philadelphia 

 has devised a diaphragm which in the main appears to be a 

 modification of the well-known English "Universal" substage. 

 This, however, was unknown to him at the time. To make it 

 he says: 



"Get a diaphragm wheel made with three large holes and 

 one smaller one ; the large hole about the size of the largest in 

 the ordinary wheel, and the smaller about 'he size of the next 

 but smallest. Now solder to each large hole a tube, say, half 

 an inch long, and into each of these tubes fit quite tightly an- 

 other tube, not tighter than that it can be easily pushed in and 

 out and keep its place, however much or little it is pushed in. 

 Into each tube tit the following lenses : — Orie of the proper fo- 

 cus as a condenser ; one with a black spot on the plane sid^ for 

 dark-ground illumination ; and a nicol in the third tube, on top 

 of which a plano-convex lens will insure extra bright illumina- 

 tion. For analyzer, use a tourmaline in a fitting which slips 

 easily over the eye-piece. The advantage of the tourmaline is 

 that you get the whole field, and not, as with a nicol over the 

 eye-piece, a field narrowed by the sides of the nicol. That is 

 all. The small hole in the diaphragm wheel serves for obser- 

 vation by ordinary light; if a stropger illurniuation is wan'.ed, 



