360 HOW TO SEE WITH THE MICROSCOPE. 



about 1-200 of an inch, direct light being used, i. e., without 

 mirror or condenser. The ease with which the duplex handled 

 this test was made amusing and apparent by my picking up the 

 stand, walking around the room, sitting it down again hap- 

 hazard before the lamp, when the resolution was found by a 

 gentleman appointed to examine to be unimpaired. This was 

 repeated three times. Will Mr. Hitchcock repeat, using a low 

 angle glass, be it a one-fifth or a one-fiftieth, and report? 



I had other tests for central light work, including histological 

 and pathological preparations. It was impossible to show all 

 of these to so many people as were present, as it was, the entire 

 evening after the readingjof my paper was occupied. Hence, it 

 will be seen that I fought the low angles on their own chosen 

 ground, and with the express view of demonstrating that the 

 very best preformance of the duplex lenses is seen by central 

 light, 



Mr. Hitchcock further says that " the universal testimony of 

 our best authorities, who have spent their lives in microscopical 

 work, is against Prof Smith." 



It was just this kind of testimony that affirmed a few years ago, 

 ths highest possible aperture of an object glass to be 135 degrees; 

 that the resolution of the Nobert 19th band was a matter of 

 faith rather than of sight, etc., etc. Mr. Hitchcock is welcome 

 to the witnesses. 



Note this fact, to- wit, in original investigations, the advanced 

 worker must necessarily be in a minority. I rejoice that some of 

 Mr. Hitchcock's witnesses have lately found cause to change 

 their opinions. Dr. Carpenter will no longer assert that the 

 resolutions of the Nobert 19th band is a k ' matter of faith, rather 

 than of sight." On the other hand, he has given unqualified 

 endorsement to the superiority of the duplex glasses. 



Mr. Hitchcock desires to ask iohy I think that most of the work 

 in histology and pathology already" done" with the so-called 

 " working lenses" of narrow angles would require further atten- 

 tion, and with wide angled glasses I reply, that in the past four 

 years great advances have been made in the construction of 

 objectives, and in the manipulation of the microscope ; what 

 was considered a " good working glass" ten years ago, would 



