ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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bands placed transversely on the glass plate forming the stage, spaced so 
that the two outer ones rest on top of the uprights and the two inner 
ones will just take an ordinary 3 in. by 1 in. slip, will be found conve- 
nient, as by this means the stage and the slip are prevented from moving 
when pressure is brought to bear on them. 
Fig. 37. 
For opaque objects the opal glass with elastic bands to take the slip 
should be used, and the light taken either directly from the lamp or 
focused by an engraver’s globe. 
For dissecting under water or other fluid, a square white earthenware 
trough fitted to one of the grooves should be used ; this can be slid in 
at various heights to suit the object. 
When dealing with balsam or other media requiring heat, a brass 
plate 10 in. long, with a narrow brass tongue 9 in. long, fixed by a nut 
and screw to the under side of the plate, should be used as a hot stage. 
The degree of heat can be regulated to a nicety according to the dis- 
tance from the stage at which the spirit-lamp or Bunsen burner under 
the brass tongue is placed. The heat is best taken with the tongue at 
right angles to the plate, as the burner is well out of the way in this 
position. The tongue folds back under the plate when not in use. 
All forms of stages can be fixed securely in the grooves by small oak 
wedges, and the dissecting trough can also be secured by cork wedges. 
Any ordinary lens-holder can be used, but a small rack and pinion, 
