171 



form which would result from placing the vertices of two 

 cones together. By this arrangement, there can be no loss 

 of motion; besides, it affords great facility in changing the 

 rod from one pin to another. 



The rod (f) is connected with the clamp arm by drop- 

 ping the notch (z), fig. 2, on one of the pins. 



The other end of the rod is attached to the lever (/), fig. 

 1. A sectional view of the mechanism for this purpose is 



Fig. 3. 



seen in fig. 3 ; (t, t), being two screws having conical points, 

 (s) a set screw for clamping to (/). 



Fig. 4. 



The pencil arm shown at (c), fig. 1, is attached to tho lever 

 (6), by an arrangement precisely similar to that seen in fig. 



