234 SUMMARY OF CURRENT RESEARCHES RELATING TO 
supported by a clamp of the Microscope-stand or is fixed to the wall 
which supports the whole apparatus. 
Lehmann’s large Crystallization Microscope.^ — Dr. 0. Lehmann 
describes the large Crystallization Microscope which he designed for 
use where great stability is required. (A more portable form was 
described in this Journal, 1885, p. 117.) The instrument is shown in 
figs. 19-21. 
For stability the base of the whole is formed of a large heavy cast- 
iron plate b b (fig. 20), which for convenience in height is let into an 
opening in the table, and rests by means of four levelling-screws upon 
two strong ledges strengthened by cross-pieces. It is pierced by 
several holes provided with screw-threads in which fit the difierent 
stands and apparatus. On the same ground of greater stability the 
movement of the body-tube is effected in quite a different manner to 
that of the ordinary Microscope. The socket which carries it is rigidly 
connected with the base-plate by a f" -formed holder (fig. 21). This 
allows the cross-arm to be very long, which renders more convenient 
the handling of the object on the stage. Since experiments at high 
Fig. 19. Fig. 20. 
temperatures, in which a large flame is used, require a considerable 
raising of the stage, and consequently a greater height of the body- 
tube than could be attained by a simple movement in the socket, the 
1“ -formed holder consists of two parts, viz. the tube, firmly screwed 
into the base-plate, and the holder proper, which slides tightly in this, 
and can be fixed in definite positions by means of a steel pin, which is 
inserted into holes bored through the holder at regular intervals equal 
to the distance through which the body-tube slides in its socket. The 
nut is then screwed on to the lower end, and the whole is as firmly 
fastened as if it consisted of a single piece. For the coarse-adjustment 
the body-tube simply slides in the socket, but the fine-adjustment is 
effected by means of a second socket, consisting of two parts, in which 
‘ Molekularphysik,’ Band i. (1888) pp. 126-33 (3 figs.). 
