320 TllK AMERICAN MONTHLY [Nov., 



MI( HOS( OriCAL APPARATUS. 



The One-Seventy-Fifth Objective. — Dr. Cutter, who i.'^ the 

 Proft .s.st>r ot" Clinical MorpholoL'V and Apjdird Medicine in the 

 College of Phy.'*icians and »Sur<.;eont? at Boston, has sent ns some 

 photof:ra|»hs of objects taken with the l-75th whicli we h(>j)e to 

 ])ublish s(Hiii. In order to use this ohjeetive, a cover-tdass is re. 

 jtlaoed witli u strip of niiea only one-two-thousandth of ;in inch 

 in thickness. Dr. Cutter has practiced niedi<nne 4) years, ami 

 has use a inicroscope nearly all of this time. 



The Griffith Microscope. — A substantial recof^nition 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. (Jriflith's 

 exhibit in the north gallery of the Lil)eral .Arts Huildimr, in the 

 gpace reserved for the Chicago Academy of 8rience, h -s been a 

 center of interest for lay as well as {)rofessional visitors at the 

 Fair. 



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

 has devi.<ed a diapluHL'm which in the main appears to l)e 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 !-maller one ; the larg<^ hole about the size of the largest in 

 the ordinary \\ heel, and the smaller about hes-zeofthe next 

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

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

 other tube, no tighter than that it can l)e easily ])ushed in and 

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

 Into each tube fit the following lenses : — One of the prop r fo- 

 cus as a comlenser ; one with a black spot on the plane sid • for 

 dark ground illumination ; and a nicol in the third tul)e. on top 

 "f whic'i 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 s 

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

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

 all. 'I'he small hole in the diaphragm wheel serves for obser- 

 vation by or«:inary light; if a stionger illumination is wan ed, 



