176 THE AMERICAN MONTHLY [Jun 
ed as follows: ‘‘Upon a movable brass plate inside a 
light-tight box is a 99° prism, mounted in such a way 
that all the light which passes through the microscope is 
projected upon a piece of ground glass at the end of a 
cone, which may be lengthened or shortened in order to 
give correct focus to the object, when it is properly fo- 
cussed upon the ground glass of the camera directly above 
the microscope. Next to the prism is a hole in the brass 
plate for allowing light to pass from the microscope di- 
rectly to the photographic plate, when the prism is moved 
by a spring and pneumatic release, and finally a sufficient 
area of the brass plate to cover the opening when expo- 
sure has been made. To take a photograph, the micro- 
scopic animal is placed in a drop of water upon a suita- 
ble glass plate, the light is turned on and the shutter so 
set that the object may be focussed upon the ground glass 
of the cone. The plate-holder is inserted and the dark 
slide drawn, leaving the plate exposed inside the camera 
bellows. The movements of the animals are easily seen 
upon the ground glass, and when the desired position is 
obtained the shutter is released, the prism moves out of 
the way and the light passes to the plate.”” The apparatus 
is not yet perfected to its inventor’s complete satisfaction 
but he states that exposures as short as one- fortieth of a 
second have been very satisfactory, and considers that 
thoroughly satisfactory negatives can be obtained with 
low-power objectives in one-hundredth of a second. The 
magnification has, however, ranged up to 200 diameters, 
Mr. Charles Baker, of High Holborn, in his last cata- 
logue, mentions a somewhat similar arrangement for in- 
stantaneous photomicrography in which a pneumatic 
shutter with a prism attachment enables the object to be 
viewed on a ground-glass screen at right augles to the 
optic axis up to the moment of exposure. Mr. Andrew 
Pringle, in his well-known book on practical photomicro- 
graphy, describes a vertical camera for the same purpose, 
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