4 o 
PRACTICAL PHOTO-MICROGRAPHY. 
one ; we have the turntable device for the microscope 
and light; a good mechanical stage ; a substage dtith 
both coarse and fine focussing adjustments, and with 
centring as a matter of course. The thinner part of 
the focussing-rod bearing the pulley fits into the thicker 
part by a square fitting; these parts are severed when 
the turntable is turned away from the axial line. 1 he 
ocular end of the tube and the front of the camera are 
each fitted with a cap ; when the image is projected on 
to the focussing screen of the camera, these caps aie 
slipped one into the other to prevent stray light from 
impinging on the sensitive plate. The base of the 
whole is a thick plank of teak, and all the parts are 
strongly clamped to this base. The microscope is first 
firmly clamped to a metal platform, from which it can 
be removed at will ; but ours is never removed except 
for “alteration or repair.” One figure (io) shows the 
instrument in position for ocular examination of the 
object down the tube ; the other (fig. n) shows it ready 
for an exposure to be made. The round finger-piece 
of the flap shutter inside the camera can also be seen 
on the right near the front of the camera. 
The ground-glass found in an ordinary photographic 
camera will not answer for focussing the image of 
microscopic objects projected upon it through an ob¬ 
jective. We use the ground-glass simply to view the 
object in a general way, to ascertain if it is in the 
centre of our plate or not; we then put in its place a 
piece of plate, or other good glass, and focus the image 
carefully on this plain glass with an eyG-piece of the 
