634 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



numbers on the pillar from 1 to 8 correspond with the numbers of the 

 lenses in the disk. 



The fine-adjustment is actuated by the milled head of a micrometer 



Fig. 96. 



screw at the base of the pillar ; this acts on a steel rod that passes up 

 the inside of the cylindrical stem, with which it is connected when the 

 pinching-screw is tightened up, so that, having made the coarse-ad just- 



