334 



H. M. JOHNSON 



and St 1 withdrawn. The head of the micrometer is calibrated to 

 read to 0.02 mm. Readings to 1 mm. are made directly from the 

 scale Sc. The journal bearing J for the micrometer screw and 

 the lugs L 1 and L 2 carry shoulders on which the upper surface of 



Fig. 4-c 

 Construction drawings for mountings. 



ring R 1 bears. The corresponding surface of the (inverted) 

 ring R 2 bears on the plane surface of H. As shown in the con- 

 struction drawings, the rings carry shoulders from their convex 

 cylindrical surfaces. The limbs of Y move in the groove formed 

 by these shoulders, while the sleeves of St 1 fits snugly in the cir- 



