328 Mayer — Experiments with Pendulum-electrometer. 



As not over 2° of deflection was used in the experiments, it 

 follows that the difference between the sine of the deflection 

 and its chord is just measurable, amounting to only }mra. for 

 an angle of deflection of 2°. The scale was inclined to the 

 horizontal so as to coincide with the chord of 2°. 



Another sphere of brass of one cm. radius was supported on 

 a rod of glass ; the latter coated, while hot, with a film of 

 paraffine. This rod was mounted vertically on a wooden base 

 which slid along a scale of millimeters on a table. This scale 

 and the one before which the pendulum is deflected are so 

 placed that when the suspended cork-sphere and the sphere on 

 the rod are just in contact the threads of suspended sphere 

 read on the upper scale, while the vertical plane through the 

 center of the sliding sphere reads 2 cm. on the lower scale, this 

 being the distance apart of the centers of the spheres. 



The ends of the thread, to which the gilded cork-ball is 

 suspended, are passed through small staples in a board fastened 

 to or near the ceiling, and are then joined together and passed 

 around a spool fixed by a screw midway between the staples. 

 By turning the spool the thread is wound on or off it, and thus 

 the height of the pendulum is adjusted so that its center and 

 that of the sphere on the glass rod are in the same horizontal 

 line. When this adjustment has been made the head of the 

 screw is tightened on the spool. 



The sphere on the rod is charged and then slid along the 

 scale on the table till it is in contact with the sphere of the 

 pendulum. The charge is thus equally distributed between 



