Induction Apparatus. — Mode ofdividijig charges. 297 



ments can be made in succession without the stem assuming 

 the least degree of charge. 



1204. Experiments should not be made by candle or lamp 

 light except with much care, for flames have great and yet 

 unsteady powers of affecting and dissipating electrical charges. 



1205. As a final observation on the state of the apparatus, 

 they should retain their charge well and uniformly, and alike 

 for both, and at the same time allow of a perfect and instant- 

 aneous discharge, giving them no charge to the carrier ball, 

 whatever part of the ball B it may be applied to (1218.). 



1206. With respect to the balance electrometer all the pre- 

 cautions that need be mentioned, are, that the carrier ball is 

 to be preserved during the first part of an experiment in its 

 electrified state, the loss of electricity which would follow upon 

 its discharge being avoided ; and, that in introducing it into 

 the electrometer through the hole in the glass plate above, 

 care should be taken that it do not touch, or even come near 

 to, the edge of the glass. 



1207. When the whole charge in one apparatus is divided 

 between the two, the gradual fall, apparently from dissipation, 

 in the apparatus which has received the half charge is greater 

 than in the one originally charged. This is due to a peculiar 

 effect to be described hereafter (1250. 1251.), the interfering 

 influence of which may be avoided to a great extent by going 

 through the steps of the process regularly and quickly ; there- 

 fore, after the original charge has been measured, in app. i. 

 for instance, i. and ii. are to be symmetrically joined by their 

 balls B, the carrier touching one of these balls at the same 

 time ; it is first to be removed, and then the apparatus sepa- 

 rated from each other ; app. ii. is next quickly to be measured 

 by the carrier, then app. i. ; lastly, ii. is to be discharged, and 

 the discharged carrier applied to it to ascertain whether any 

 residual effect is present (1205.), and app. i. being discharged 

 is also to be examined in the same manner and for the same 

 purpose. 



1208. The following is an example of the division of a 

 charge by the two apparatus, air being the dielectric in both 

 of them. The observations are set down one under the other 

 in the order in which they were taken, the left hand numbers 

 representing the observations made on app. i. and the right 

 hand numbers those on app. ii. App. i. is that which was 

 ori finally charged, and after two measurements, the charge 

 was divided with app. ii. 



App. i. App. ii. 



Balls 160° 



0° 



