370 HOW TO SEE WITH THE MICROSCOPE. 



aperture and has greater working distance than my own one- 

 tenth ; its work over such tests as the Nobert and Moller (balsam) 

 plates was quite equal to that of its formidable competitor, 

 while the views it gave by central light were simply glorious, 

 excelling the old one-tenth. This, as a first attempt on the part 

 of a young optician, is truly encouraging. These new duplex 

 glasses will receive my earnest attention, and I may have, in the 

 future, something more to say about them. 



Allow me to further state, that, being desirous of acquainting 

 myself with the work of our own opticians, I wrote to the 

 Rochester firm, asking the loan of objectives for examination 

 and study. They responded promptly, sending me by return mail 

 a full line of Mr. Gundlach's lowest priced " Student's" work. 

 They certainly had no time to select exceptional glasses. My 

 time has been so thoroughly occupied, I have not yet given them 

 the attention they deserve, but as far as they have been examined 

 J am much pleased with them a three-fourth inch at $6, a one- 

 half inch at $8, and a three-tenths at $11 , are very finejindeed 

 for their cost. 



ANGULAR APERTURE ONCE MORE. 



Ed. Am. Jour. Microscopy. The discussion between Prof. 

 Hitchcock and myself, which, during the last few months you 

 have done us the honor to print, seems to have become some- 

 what of a rambling nature. Prof. Hitchcock " changes base " 

 so often, that it would bother a streak of lightning to catch 

 much less corner him. Be this as it may and perchance he 

 might return the compliment, 1 can only say that I have endeav- 

 ored to stick to the points at issue the merits of high, as com- 

 pared with low angles, I have attempted to set forth from a 

 practical standpoint, being tolerably familiar with the use of 

 either style of glass. 



I have tried my best to have Prof. Hitchcock examine high- 

 angled glasses for himself, and report results, but, as your read- 

 ers are aware, from his own assertions, Prof. Hitchcock does 

 not claim a practical knowledge of them, and as a matter of 

 course he cannot see what that " handling " (of which it will do 



