1899] MICROSCOPICAL JOURNAL. 27 



one would readily assent to any statements he mig-ht make 

 concerning- actual observation of the results obtained by 

 him. Perhaps a sug-g-estion can be made in passing-, and 

 that 13 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 so/e/y an in- 

 crease in amplification (over that of a sing-le microscope); 

 and further, because increase in amplification beyond that 

 easilv obtained with a sing-le microscope, // fiof accompanied 

 with a proportionate increase in resolving po^cer, is practically use- 

 less. What users of the microscope most urg-ently 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," T^rans. 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 photog-raphs of an 

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

 of Photography and 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. 



