for Testing Camera Lenses. 



781 



Flange. The lens holder is screwed to take the Royal 

 Photographic Society's 6 in. diameter thread. The maximum 

 aperture which can be examined is 5Jin., and the largest lens 

 mount which the holder will accommodate is 7 in. maximum 

 diameter. 



Details of the Apparatus. 

 The annexed figures show the apparatus. 



Fig. 4, is a general view. (See PI. XXIV.) 



5, is a plan. 



6, a. side elevation. 



7, a side elevation o£ the mirror carriage. 



8, a side elevation of the mirror carriage and cross- 

 bar carriage. 



9, an end elevation of mirror carriage. 



Fig. 

 Fig. 

 Fig. 

 Fig. 



Fig. 

 Fig. 



10, plan of adjustment for crossbar carriage. 



Fig-. 5. 



The rotation of the lens carriage is effected by means of a 

 bar, 105 (fig. 6), parallel to the axis of the lens and extending 

 to the outer edge of the interferometer. A scale and index 



