1086 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Now though the ohjcct-carricr can of course only movo vertically, 

 the clamp frame is provided with motion in two directions, viz. from 

 side to side and from heforo backwards. These movements aro 

 effected through the mediation of the endless screws o working 

 against a thread on the half-circles it (figs. 241, 242). 



Tho micrometer-screw a, capable of moving 30 mm., is turned hy 



Fig. 242. 



the large milled head d. This head is marked by 100 radial lines, 

 and as one turn of the screw raises the object 0*5 mm., one division 

 corresponds to " 005 mm. 



The pointed upper end of the micrometer-screw pushes against an 

 agate plate q fixed to the lower end of a rod p, let into the cross-bar 

 of /x ; below the latter is a metal case n and a fixing screw. The 

 lower end of a is in connection with the bars b and c, which in their 

 turn are in apposition with D. 



