Electrieity on Separation of Parts. 378 
tween the rubber and the points of the conductor in ma- 
chines of the common construction was injurious in its 
_ effects, not only in causing the dispersion, in part, of th 
electricity excited, but by uselessly wasting the excitin 
surface, Plates were therefore mounted in a very cor 
pact and perfect manner, with three pairs of rubbers pla- 
ced at equal distances from each other; the conductor 
also had three arms, furnished with points a little in ad- 
vance of each pair of rubbers, to collect the electricity in 
the usual manner. The rubbers were not attached to a 
surrounding frame, but to brass arms, which, proceeding — 
rom a socket through which the axis passes, diverged 
from equal distance from each other, towards the periphe- 
ry of the plate. The machine has a very compact and 
neat appearance, and its various smaller parts are contriv- 
ed with much judgment. 
In some comparative experiments made with a plate 
twenty-two inches in diameter, the superiority of three 
pair of cushions over two pair was very manifest. In the 
following table the first column expresses the length in 
inches of the rubbers; the second, the length of the spark 
_ when two pair of rubbers were used and the third, the 
length of tl rk when three pn of rubbers were on. the 
machine, _ : 
6 inches. 12 inches. 18 aula : 
Pins bq 2 
Be tt 16 1 py ee 
9 ce 18 ce OT se 
10 = 6 20 se 30 “i 
fla te af ee were S dicnctly ey by tearing quick- 
ece of cotton cloth. Edin, Joure 
