630 Transactions of the Society. 



if a movable stage does not exist a temporary one could be easily 

 made by having a brass plate moved by the screw itself), no other 

 micrometer at all being needed. 



I have used it on two laboratory Microscopes for a variety 

 of measurements. It takes only a minute or two to set up the 

 apparatus. 



Given delicacy of touch, measurements can be made of any- 

 thing visible. I have found no difficulty in reading to £ micron. 



If a capstan-pin be inserted into the edge of the milled head 

 of the screw, a more delicate angular movement may be given to 

 the screw, and readings of T \, micron obtained. 



