20 THE AMERICAN MONTHLY TJau 



little light, the bull's eye should he used focused upon the 

 specimen, care being taken to avoid glare or excess of il- 

 lumination which will result in a confused image in the 

 negative. With some subjects the Lieberkuhn may be 

 used advantageously, with others the parabolic reflector, 

 but the majority yield better results under the most sim- 

 ple forms of illumination. A very little practice will en- 

 able the operator to determine this for himself, in widely 

 differing cases. 



The character of plates to be used for the negatives is 

 probably of more importance than those for transparent 

 objects. They should be of a good degree of sensitive- 

 ness but not too rapid, must be capable of giving great 

 density if desired and should develope equally well with 

 all mediums, so that the worker may employ that with 

 which he is most familiar. The best and most satisfact- 

 ory paper I have ever used is the "Velox," a modified bro- 

 mide, capable of being handled by daylight but sensitive 

 enough to be printed by lamp or gaslight, and giving 

 black and white prints of the most exquisite and perma- 

 nent qualities. "Glossy Velox" I have found to yield re- 

 sults superior to those obtainable on the matt surface. 

 Some specimens are better delineated by allowing the 

 light from the sky to fall as nearly perpendicular as pos- 

 sible upon them. Others again show better by throwing 

 the light obliquely across their surfaces by means of the 

 bull's eye condenser or parabolic reflector. They should 

 always be carefully studied under various methods of il- 

 lumination before making any attempt to photograph 

 them, in order to determine upon the best resolution and 

 definition of their several features. The light reflected 

 from a white cloud and falling directly upon the object 

 without the intervention of a condenser is best. Lighted 

 from the same source, but with a condenser so arranged 

 as to throw the light across their surfaces, causing light 

 shadows gives good results. 



