32 
PRACTICAL PHOTO-MICROGRAPHY. 
power simple work will save much worry, and much 
failure, by providing himself with an apparatus made 
for the purpose, however simple and unpretentious. 
Anyone possessing a suitable microscope, a camera of 
fairly long stretch, and a lamp, may, with a little 
ingenuity, and a little joiner-work, construct a very 
good apparatus for himself. But as almost all op¬ 
ticians now keep in stock suitable apparatus, at very 
reasonable prices, it is probably the safer, and possibly 
the cheaper, plan to obtain one of these apparatus. 
The leading point of such an apparatus is that the 
light, the axis of all the optical parts, and the centre of 
the plate, shall be, in the “ normal ” position, in one 
line ; the plate and the stage parallel to each other, and 
at right angles to the optical axis of the system. The 
stage, or the preparation on it, the condenser, the bull’s 
eye, and the radiant have a certain amount of possible 
movements, vertical and horizontal, and the plate may 
also be movable in a direction vertical to the optical 
axis, but at all times the plate must be parallel to the 
stage; and the optical axes of the objective, the tube, 
and the ocular remain fixed at all times. 
The camera should be capable of being stretched to 
the length, from front to back, of at least 30 inches; if 
much work is to be done without the ocular the stretch 
may extend to 60 inches. Though, as a rule, the nega¬ 
tives made are not larger than a circle of 3111. diameter, 
still the size of camera usually supplied for the work is 
“ half-plate,” 6J by 4! inches. This larger size is occa¬ 
sionally desired, but in our practice very seldom, and 
