228 E. Emerson on Improvements in the Photographic Camera. 
ho use a magnifying glass and a smaller diaphragm 
Those w 
succeed better, but by neglecting to reduce the diaphragm toa - 
minimum, their results are by no means as perfect as they might 
" e aid of acommon magnifying-glass one and a half 
inches in focal length, with which to view the image on the ground 
glass of the camera, and an aperture of two-fifths of an inch in 
the diaphragm in taking the negative, I was able without any 
difficulty, to obtain results fully equal in point of sharpness, to 
4s ste upon it. This last proved an insuperable bar to any 
made with two objects in view,—1st, to carry up the power of 
the focusing lens, and, 2d, to subsitute for the ordinary grout 
glass of the camera something of finer texture so as to stand the 
| y 
had seen produced by the professional photographers. Indeed, 
among both British and American artists and amateurs 12 pho- 
microscope. he 
_ At this stage of the investigation Prof. Rood constructed 1F 
me a compound microscope of a power of thirty d 
which I hoped to be able to employ as a focuser. Its for 
construction will appear from the following diagram, fig. 1. 
3 
sametel = 
rm an 
: 
