THE AMERICAN 



MONTHLY 



MICROSCOPICAL JOURNAL. 



VOL. XIX. JULY, 1898. NO. 7. 



Contents. 



Microscopic Images and Vision 109-124 



PracTicai. Suggestions. — Cicada tredecem, a White Fish's 



Stomach, Bazania 125-126 



Editorial. — Postal Microscopical Club 126-127 



Science Gossip. — Preserving Media, Astronomy, Woods 127-128 



Microscopic Images aud Vision. 



By lewis WRIGHT. 

 (Concluded from Page 104.) 



15. We therefore next consider that illustration. 

 To begin with, the resolution of A. pellucida is no renl 

 problem at all: it is not even of the same nature as 

 the problems which do confront the scientific worker. 

 Supposing it were, the latter would regard with con- 

 sternation the elaborate apparatus described for produ- 

 cing monochromatic light. This diatom, however, has 

 been studied for many years ; the dimensions of its 

 structure are known and familiar; and the powers of 

 annular illumination have long since been ascertained. 

 It is no problem, or one in which help is needed, to take 

 what is really a " grating " of this known fineness, and 

 already knoion to have this definite periodicity of struc- 

 ture, aud arrange matters so as to get the most conspicu- 

 ous " resolutioii " of it. The problems in which assist- 

 ance is really wanted, the microscopic worker's really 

 •' difficult " objects, are such as Dr. Dallinger confronted 



