1858.] on Static Induction, 491 



force differs in degree ; or else errors of the same kind as those 

 described with the ball inductric will occur. It should also be 

 so used as to receive no charge by convection. When introduced 

 between the inductric and the sulphur, it is very apt, if the charge 

 be high, or if particles adhere to the inductric, to receive a charge. 

 This is easily tested by introducing the carrier into its place, 

 abstaining from touching the gold-leaf, withdrawing the carrier, and 

 examining it : it is not until this can be done without bringing away 

 any charge that the carrier should be employed to touch the gold- 

 leaf surface, and bring away the indication of its electrical state. 



As before said, if when the state of matters is perfect, and no 

 convection interferes, the gilt sulphur be put into its place, left 

 there for a short time, and brought away again, it will be found 

 without any charge .either of the gold-leaf coating or the sulphur. 

 If it be put into place, the coating next the inductric be uninsulated 

 for a moment only, and the plate brought away, that coating will 

 then appear positive. If it be put into place and the further gold- 

 leaf be uninsulated for a moment, that coating when the plate is 

 brought away will be found negative. These are all well known 

 results, and will always appear if convection and other sources of 

 error be avoided. ^ 



22nd March, \%S^. .M. F. 



