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Description of an Object-compressor for Preparing and 
Mounting Objects. By W. Hislop, Esq. 
(Read June 25tli, 1856.) 
This little instrument I have found extremely useful in the 
preparation and mounting of various substances as micro- 
scopic objects. It is so contrived as to afford a graduated 
pressure without the risk of breaking the glass cover. Any 
who have tried their hands at mounting objects permanently 
will at once see its applicability for all cases where a constant 
pressure has to be maintained for any time. For instance, 
if a section or other preparation is required to be mounted 
in balsam_, it is necessary to keep the cover down until the 
balsam is cold, or the section will frequently curl, and lift it 
so as to admit the air ; and this will sometimes occur even 
then. My plan is to have several of these compressors at 
hand, and as soon as the object is properly placed in the 
balsam, and the cover put on, the slide is at once placed 
beneath one of them, the trigger is let gently down, and the 
adjusting screw turned upwards, till all the superfluous balsam 
is expressed. The slide, still under the compressor, is then 
put aside in a drawer, until the balsam is hard enough to be 
safe. In like manner I apply it to the mounting of objects 
in fluid, being able to lay a coat of cement around the cover 
while it is under pressure. Previous to mounting, I also find 
it useful for flattening substances of all kinds, especially when 
being dried for mounting in balsam. 
The figures show two forms of the compressor. Eig. 1 
VOL. V. 
rig. 1. 
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