54 



BRUSH— KINETIC THEORY OF GRAVITATION. 



It is essential that the centers of gravity of the weights be exactly 

 the same distance above their supporting pins. To assure this, each 

 weight was adjusted to have its center of gravity exactly midway 

 between its upper and lower ends by the following procedure : The 

 pendulums having been started swinging with a definite amplitude 



Fig. 2. 



and brought to synchronism by length adjustment, one of the 

 weights was turned over ; this at first resulted in loss of synchronism 

 at the same amplitude. Then, as indicated, the upper or lower 

 cylindrical portion was slightly reduced in diameter by turning off 

 or sandpapering in the lathe. Again the pendulums were synchron- 

 ized, and again the same weight was turned over and synchronism 

 tested. This process was repeated again and again with each weight 

 until either could be turned over without affecting synchronism in 

 the slightest observable degree. In making these adjustments very 

 minute departure from synchronism could be detected in half an 



