Electric Dust Figures. 



2G9 



frequency In the discharge circuit of the jars A and B 

 through E was constant. D is simply a conductor of high 



inductance for charging the jars. The energy of the discharge 

 at E depends, however, on the length of the primary spark- 

 gap 0. As C increases the energy of the discharge at E, 

 and therefore the intensity of the sound of the spark, 

 increases. This spark E was shielded from the primary spark 

 C, and was used to produce the figures. 



The distance between two consecutive ripples was measured 

 for four different lengths of the primary spark, the results of 

 which experiment are shown in the following table. A large 

 16-plate Wimshurst machine presented by Lord Armstrong 

 to the Armstrong College was used. 



Length of the 

 primary spark. 



Distance apart of two 

 consecutive ripples. 



1 inch 

 1| inches 



2 „ 



^2 " 



0'893 mm. 

 1-04 „ 

 114 „ 

 118 „ 



From this table it is seen that, although the frequency of 

 the electric oscillation is kept constant, the distance apart 

 of two ripples varies, and in fact increases as the intensity 

 of the spark increases. 



Taken in conjunction with a result from Richmond's 

 experiments that the distance apart of two consecutive ripples 

 increases as the diameter of the powder increases*, one must 



* Richmond, he. cit. 



