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SUMMARY OP CURRENT RESEARCHES RELATING TO 
a milled head fixed to a screw having a hardened steel point, acting on a 
lever, in a perfect fitting dove-tail slide, about 2^ in. long. The prin- 
ciple of it is shown in the accompanying figure (fig. 3). 
At first si glit it would appear that the screw controlling this important 
movement has to bear the entire weight of the body of the instrument, 
Fig. 4. 
as in the Continental models. This is a common error, but not in 
accordance with fact. The turning of the milled-head screw actuates a 
hardened steel lever B, varying in length according to the size of the 
instrument, the fulcrum C of which is placed as closely as possible to 
the sliding fitting in which the movement of the body takes place, which 
reduces the weight carried by the milled head to considerably less than 
