98 On the Generation of Statical Electricity. 
will then be produced, both in the exciting point of the rubber 
and in the corresponding portion of glass surface ; by hypothesis, 
the molecular vibration of the rubber producing negative, and that 
of the glass, positive electricity, each within itself. If it be sup- 
posed that the portion of the surface of the glass, in this indefi- 
nitely small movement, has continued in contact with the exciting 
point of the rubber, then the two electricities, respectively gene- 
rated in each, will combine or interfere, and a neutral state will be 
the result whilst such contact continues. But should this por- 
tion of glass in its further movement pass beyond the exciting 
point, its molecular vibration continuing for a certain period, will 
evolve an additional quantity of positive electricity, which will 
remain after the molecular vibration has ceased ; and this portion 
of glass will be electrically excited. Should the movement be 
still further continued, and this excited part brought into contact 
with the consecutive exciting point of the rubber, its electricity 
will, by the influence of this point, be nearly if not entirely neu- 
tralized. For otherwise it is difficult, if not impossible, to con- 
ceive of the evolution and absolute contact of the two electrici- 
ties, at such point, without combining or interfering. 
This view of the subject being taken, it follows, that only the ‘ 
last exciting points of the rubber produce the effective result. 
This, on first appearance, isa startling conclusion, as it apparently 
reduces the rubber to a mathematical line; on examination, how- 
ever, this is found not to be the case; there must be a certain 
number of these last exciting points, in each of several consecu- 
tive parallel lines, as the points necessarily have spaces between 
themselves; hence a portion of electricity excited on the glass 
may pass between several, before it emerges entirely from the 
rubber. It follows, therefore, that a certain breadth of rubber is 
necessary, although it must be comparatively small. With rub- 
bers, properly constructed, as will be described hereafter, the max- 
imum effect for the larger machines, was produced by rubbers 
one fourth of an inch in breadth; and for the smaller, one eghth 
of an inch; the smaller rubbers having generally a greater pres- 
sure. 
To determine the above, as well as to ascertain and confirm 
all other results given in this paper, a numerous set of experi- 
ments was instituted, by means, principally, of three machines. 
One was a glass plate of 12 inches, previously alluded to; one a 
