50 
PRACTICAL PHOTO-MICROGRAPHY. 
objects of various sizes. The lamp, paralleliser, and 
stage slide backwards and forwards, controlled by 
guides which preserve the rectang-ularity of the move¬ 
ment. The camera takes a whole-plate slide, but this 
is provided with several inner carriers, so that various 
sizes of plates are usable. Both the front and the back 
Fig. 15. 
of the camera can be moved backwards and forwards, 
the total stretch available being 30 inches from front to 
back. The front is provided with apertures threaded for 
microscopical objectives and others with the standard 
thread, as well as for any ordinary photographic lens of 
reasonably small size. The tube carrying the lenses 
has a coarse rack adjustment such as that of a micro¬ 
scope, and also a liner, but not very fine, adjustment D. 
With these low magnifications it would be very difficult 
to focus accurately with a really fine motion. The 
image is generally first placed, roughly focussed, and 
