1899] MICROSCOPICAL JOURNAL. 21 



one would readily assent to any statements he might make 

 concerning- actual observation of the results obtained by 

 him. Perhaps a suggestion can be made in passing, and 

 that is to call attention to the saying-. 'By their fruits ye 

 shall know them'. People are a little suspicious of too tall 

 claims. No one is suspicious of actual demonstrable re- 

 sults, and those are not yet forth-coming- so far as I have 

 seen." — S- H. Gage. 



Amplification is not Resolution. — "I regret to say that 

 my impressions regarding the instrument are most unfa- 

 vorable. Why? Because the result obtained is solely an in- 

 crease in amplification (over that of a single microscope); 

 and further, because increase in amplification beyond that 

 easily obtained with a single microscope, if vol acco?npanied 

 with a proportionate increase in resolving power, is practically use- 

 less. What users of the microscope most urgently want to- 

 day is increase in resolving power. This only increases 

 with what Prof. Abbe has termed numerical aperture. 

 Doubling, or trebling, a microscope in no way increases 

 numerical aperture and, therefore, in no way increases re- 

 solving power. The writer has used methods similar 

 to those used by Mr. Gates. Photos 14 and 18, for instance 

 illustrating "An Experimental Study of Aperture as a 

 Factor in Microscopic Vision," Trans. Am. Microscopical 

 Society, 1896, were taken with essentially a double micro- 

 scope. The idea is not new to others, although new to him. 



In 1892, the writer applied the idea in astronomical pho- 

 tography, using a portrait lens instead of one of the mi- 

 croscope objectives. Great amplification (for portrait lens) 

 was obtained (as with the Gates double microscope). Res- 

 olution, however, was wanting (as with the Gates double 

 microscope). An account of this apparatus and of the de- 

 fects in its products, illustrated with photographs of an 

 eclipse of the sun, may be found in The American Annual 

 of Photography a?id Photographic Times Almanac 1897, P. 155. 

 Corresponding defects, as to resolving power, are insepa- 

 rable from the products of the Gates' double microscope 

 camera." — A. Clifford Mercer. 



