BRUSH— A KINETIC THEORY OF GRAVITATION. 



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through which the rod passes. The upper part of the rod is slightly 

 flattened on one side by grinding, and a thumb screw in one end of 

 the knife-edge block bears against the flattened side of the rod and 

 clamps it firmly in the block after each length adjustment is made. 

 The knife-edge, ground true and sharp, rests in the plate groove 

 above described, while the rod passes downward through an opening 

 in the side of the plate. 



Each pendulum rod terminates at its lower end in a straight brass 

 rod 13 cm. long and 0.4 cm. diam. A perfectly straight horizontal 

 steel pin passes loosely through the brass rod near its lower end, and 

 on this pin the cylindrical bob, or weight as I shall hereafter call it, 

 rests. 



Fig. I shows the upper and lower parts of one pendulum in detail, 

 with the bismuth weight in place. 



Bi 



Fig. I. 



The brass rod at the lower end passes just freely through the 

 weight, and accurately in its axis. A weight is easily removed from 



