G, Palache — Crystal Measurement^ etc. 



287 



certain part of the horizontal circle; and of the centering and 

 adjusting devices. The centering device enables the move- 

 ment of the crystal in three rectangular directions, by means 

 of which it may be brought into the intersection of the two 

 axes Aj and A^. The adjusting device is a ball-and-socket 

 joint like that of the contact goniometer, or an ordinary tipping 

 table. 



The vertical circle is represented by the bent arm B revolv- 

 ing about the axis A^ in a plane perpendicular to H. It can be 

 clamped at any point and carries a graduated segment of a 

 circle, Y. The arm B carries the collimator C and the tele- 

 scope F ; and between them, in their plane and bisecting their 

 angle CF, a rod N with needle point n. N can be shoved 

 down in its bearing until the point reaches the paper, where it 

 marks the point of projection. 



The light is carried to the collimator from the lamp* by 

 means of the broken tube K, in which are two mirrors ; in all 

 positions of the arm B the light follows the collimator. The 

 needle JS" moves with the arm B about the axis A^ and in a 

 plane normal to H. Its arc is 90°, from vertical to horizontal, 

 and the point is always directed to the same side. On this 



*For the construction of this lamp see Zeitschr. fiir Kryst,, 1894, xxii, p. 149. 

 It employs the Welsbach light, gives an intense light for the signal and has a side 

 opening with mirror which gives light for reading the vernier and entering notes. 

 It is made by P. Stoe. 



