676 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



The arrangement of the apparatus is shown in fig. 161. A strong 

 pillar B B rises perpendicularly from the base and bears a pivot D, 

 round which is a movable arm C, whose (partial) rotations give the 

 lateral inclinations of the camera. The angle of inclination can be 

 accurately read off to £° on the scale at F. The screw B serves as 

 a clamp. The coarse adjustment of the objective is effected by a push- 

 motion of the lower part of the camera on the pillar T ; the fine adjust- 

 ment is by rack-and-pinion. When a stereoscopic plate is to be taken 

 a pin is thrust through the hole visible in D, and its point accurately 

 marks the inclination axis. The camera is, however, first brought into 



Fig. 161. 



the proper position for the negative and is clamped by the screw /, as 

 the pin must also pass through a hole in the pivot of F. The point of 

 the pin, as well as the objective, is now finely adjusted, and, by means 

 of slight lateral movements of the objective board combined with 

 slight push movements of the pin, is brought into the centre of 

 the focussing screen. The frame is so arranged that the perpendicular 

 to the centre of the screen intersects the rotation axis. When the 

 image of the pin-point has been thus sharply defined in the centre 

 of the screen, the objective is orientated and the pin drawn out. The 

 stage with the object is then so orientated on the foot-plate that the 



