and Laboratory Methods. 



1991 



first used at these lateral joints, but is now dispensed with, as it was found that it 

 did not allow sufficient play for the expansion and contraction of the glass inci- 

 dent to changes of temperature in the room. The top of the case is held in position 



Fig. 1 — An outline of exhibition microscope and lass case ; a, set-screw for fastening the 

 ocular ; d, clamping ring for fastening draw-tube ; c, block of brass inserted between 

 arm and the lower support; (/, upright metal rod; ■.-, flange of metal collar. 



by four hollow, upright metal rods which pass through the wooden base and 

 at the top through processes of the metal collar. The top is fastened to the rods 

 by key-screws, with rubber washers, and screws also fasten the rods on the under 



