392 Scientific Intelligence. 
rest could not at any rate become considerably charged without 
discharging themselves by very short sparks from one to the other. 
Two electrified plates, each having the form of a sector of a cirele, 
but which did not reach to the axis, were placed, opposite to 
one another, above and below the rotating plate. Under these 
there were in each ring two paths open, between h 
have divided itself in the inverse ratio of their resistances. Ifthe 
inducing sector comprises | of the circumference, the resistance 
of the path in the sector is to that of the path outside of it as 
1:n—1; and therefore ”“—! of the current returns through the 
n 
sector, and + outside of it. In the sector a quantity corresponding 
n 
to the sum of the two currents is carried forward against ne 
current by convection. If, then, a convective motion of electri¢ y 
