236 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
tube serves to convey a stream of air for cooling the preparation. The 
tube is closed, and consequently the air cut off, by means of a conically 
pointed screw on the opposite side of the pillar. 
For measuring extinction angles and angles of crystals, &c., the 
Microscope is provided with cross wires. In order that the axis of 
rotation of the stage should pass exactly through the centre of the 
cross-wires, the cross-piece of the 1“ -formed arm is not rigidly con- 
nected with the vertical column, but only by means of a nut screwed 
Fig. 21. 
firmly on. The opening through which the spindle of the screw passes 
is somewhat larger than it, and the latter is square below. Against the 
faces press four screws set in the cross-piece at angles of 90° to each 
other. As is seen from fig. 20, the required adjustment can be effected 
by suitable movement of these. In order to be able to fix the form of 
the object a drawing-board U (fig. 21) is set up obliquely behind the 
Microscope, a small three-sided prism being fixed to the eye-piece. 
Two raised portions on the table serve to support the arm during 
drawing and observation. 
Konkoly’s Microscopes for the Cameras of Telescopes.* — Dr. N. v. 
Konkoly uses a compound Microscope for focusing the image produced 
* Ceutral-Ztg. f. Optik u. Mecb., x. (1889) pp. 229-32 (6 figs.). 
