Effect of Electrical Convection, 



193 



coating of ihree of the jars. The outside coatings were 

 earthed. It was found convenient to drive the reverser at 

 a speed of from 3 to 5 revolutions per second. The charge 

 on the disks was therefore reversed 12 to 20 times a second. 

 As the disks and condensing-plates formed a condenser of 

 considerable capacity, it was therefore found necessary, in 

 order to keep up the potential of the battery, to keep the 

 Voss machine running at a considerable speed, in fact as 

 fast as the construction of the machine permitted. This 

 was accomplished by means of a small electric motor, the 

 speed of which remained admirably constant. When the 

 disks were being charged the potential seldom varied over 

 3 per cent. 



General Arrangement of the Apparatus. — This is shown in 

 iig. 2. The letters indicate the following : — 



E, an absolute electrometer. 



D, disk apparatus and coil. 



M 1} motor driving disks. 



M 2 , motor driving Voss machine. 

 Phil. Mag. S. 6. Vol. 2. No. 8. Aug. 1901. 



