1900.] 



on Recent Studies in Gravitation. 



283 



There is another mode of proceeding which may be regarded as the 

 Cavendish experiment turned from a horizontal into a vertical plane, 

 and in which the torsion balance is replaced by the common balance. 

 This method occurred about the same time to the late Professor U. 

 Jolly and myself. The principle of my own experiment * will be 

 sufficiently indicated by Fig. 3. A big bullion balance with a 4-foot 

 beam had two lead spheres, A B, each about 50 lbs. in weight, hanging 



Fig. 3. — Common Balance Experiment (Pointing). 



from the two ends in place of the usual scale pans. A large lead 

 sphere, M, 1' in diameter and weighing about 350 lbs., was brought 

 first under one hanging weight, then under the other. The pull of 

 the lead sphere acted first on one side alone and then on the other so 

 that the tilt of the balance beam when the sphere was moved round 

 was due to twice the pull. By means of riders the tilt and therefore 

 the pull was measured directly as so much increase in weight. This 

 increase, when the sphere was brought directly under the hanging 



Phil. Trans. 182, 1891, A, p. 5G5. 



U 2 



