PHOTO-MICROGRAPHIC APPARATUS. 
33 
it is always easy to produce, or to get produced, an 
“ enlargement ” from the smaller size to the larger 
without any serious loss of quality. When the camera 
is of half-plate size, the usual plan is to have in the 
“ dark slide ” a “ carrier,” by which we use in our larger 
slide a smaller plate, such as a “ quarter-plate,” \\ by 
3l inches, or, as some prefer, 3-4 inches square. The 
latter size takes all that we usually require, but does 
not allow so much room for writing on the negative as 
does the full quarter-plate size. The dark slide must 
not slide into the camera by long grooves, but by a 
“ bayonet ” joint, and it should go into position very 
easily, otherwise the focus may be disturbed at the 
critical moment. 
Cameras with such a stretch as 30 inches are gene¬ 
rally made with bellows for the body, and this is the 
best system ; the bellows need not be of line leather, 
“ cloth ” bellows answer quite well. The bellows 
should be supported in some way about the middle, 
so that they may not “ sag ” and interfere with the 
projected image when a long camera is being used. 
At the front of the camera, just behind the end 
of the microscope tube, there should be a shutter 
inside the camera, working easily, and operated from 
the outside by a milled head screw or other handy 
device. This is for starting and closing the exposure. 
The back of the camera may have a rise and fall, 
and a side motion, so that the image may at any 
time be made to fall exactly on the centre of the plate, 
but this is rather a luxury than a necessity. The 
