24 
which fit tightly into the small holes usually made in the 
upper part of the movable stage of all microscopes, so as to 
keep the plate firmly fixed to the stage of the microscope. 
The compressor (K, I, H, M, N) is turned off the stage, 
and remains in that position when not in use. It consists 
of a stout arch of brass terminating in two feet, one (H) on 
which it pivots and which should be. made stout and strong, 
the other foot (k, 1) ends in a shoe with a spring catch (1), 
and which, when the compressor is turned round on the 
pillar (H), fits into the notch (c), and can be released by the 
finger acting on the pin (x); the compressing plate (m, n) is 
acted upon by the milled head (P), and can be lowered and 
raised to any extent required by a micrometer screw to 
which it is attached. 
With the compressorium fixed on the stage of the micro- 
scope (the compressor turned off as in the dotted lines) every 
kind of microscopic work can go on just as well as if the 
compressorium were off the stage; in fact, it is not at all in 
the way; however, when anything requiring compression 
turns up in microscopic research the compressor part can be 
pivoted round the pillar (#) so as to occupy the position indi- 
cated in the continuous lines, and that without disturbing the 
slide, cover, or object-glass (although a little retraction of the 
object-glass may be made in order to see what you are about), 
and then by turning the milled head (Pp) the plate m, N, is 
