214 SELECTION AND "USE 



The other self-centering turn-table was invented by Mr. C. 

 F. Cox, of New York, and is shown in Fig. 66. The slide is 



Fig. 66. COX TURN-TABLE. 



grasped by two angle-pieces, which are simultaneously moved 

 to and from the centre by means of a right and left hand 

 screw. When it is desired to re-varnish slides which have 

 not been accurately centered in the first place, a pair of spring 

 clips, attached to a stout bar, are fastened on. This can be 

 effected in an instant. The arrangement is shown in Fig. 67. 



Fig. 67. COX TURN-TABLE. 



There is also a very ingenious device for placing a row of 

 small cells along the middle of a slide. This consists of two 

 equal right-angled triangles, the square corners of which fit intg 



