MICROSCOPIC OBJECTS. 



II 



gave a fair negative. All objects are not 

 fitted for photography; therefore it may be 

 taken as a rule that if any object bears an 

 exposure of half an hour with any lens, 

 without being fully exposed, it is simply 

 useless to attempt it. There is a little 

 scarlet mite common in gardens, the scarlet 

 Tiornbidium, which, owing to its color, 

 may be exposed for any period without get- 

 ting any better photogiaph than a blank 



outline. Such objects should, if possible, be 

 bleached before attempting to photograph 

 them. 



When magnesium ribbon is used as the 

 source of light, the exposures become very 

 rapid. The writer has never used this 

 light with low powers, but he has found ten 

 seconds to fifteen seconds ample for di- 

 atoms with the -,-\j-inch objective. 



The dry plates recommended for photo- 



WING OF MIDGK (pSVCHODa). 



micrography are the most rapid in the 

 market. The writer has used Swan's ten 

 times collodion, and thirty times collodion ; 

 and while the ten times are excellent for 

 low powers, he still prefers the thirty times 

 plate for every purpose. He has also used 

 plates still more rapid, and found them sat- 

 isfactory in every way. Very rapid plates 

 are often difficult to manipulate when used 

 for landscape work, but when used for pho- 



to micrography they become as easy to de- 

 velope as any sIo a' plate, while they have 

 the great advantage of increased rapidity. 

 The writer is not alone in advising the use 

 of rapid plates, for the author of Practical 

 Microscopy has obtained good results on 

 Swan's fifteen times plate, while Dr. Stern- 

 berg, one of the most experienced and ac- 

 complished of living photo-micrographers, 

 uses Eastman's instantaneous dry plates. 



