On the Generation of Statical Electricity. 95 
tion of the points of the glass and rubber, at the first and second 
consecutive. moments of action, evidently continues during the 
entire period of operation. 
From what has preceded, two primary objects are to be attain- 
ed: first, to determine the best method of disposing of the nega- 
tive electricity of the rubber ; second, to obviate the injurious ef- 
fects of those of its parts not in contact with the glass. 
To attain the first object, it naturally suggests itself to conduct 
it off by forming a communication with a conductor between the 
rubber and earth; and consequently, the directions given, and 
carried out in the construction of the best electrical machines, 
have been, to form a metallic connection with the back of the 
rubber, and the surrounding conducting objects. The idea ap- 
pears not to have occurred, that such communication should be 
made with the metallic face, in place of the back of the rubber. 
The cushions being made of non-conducting materials, as sill or 
leather, stuffed with similar substances, the faces of the rubbers 
are insulated, and the negative electricity is prevented from es- 
caping freely. ‘This insulation is so complete in some rubbers, 
that with a twelve-inch plate machine scarcely the smallest quan- 
tity of electricity could be obtained, until the amalgam faces of 
the cushions were connected by a wire with the floor, when its 
amount was suddenly and greatly increased. It has been inter- 
esting to observe the numerous near approximations to this result, 
which, however simple, appears not to have been exactly hitherto 
attained ;—the nearest approach, probably, being the suggestions 
to stuff the rubbers with elastic fragments of metal,* and the prop- 
Osition to moisten their interior substance.} 
Electrical excitation, in all descriptions of apparatus made use 
of for that purpose, will be increased by adopting the preceding 
suggestion. Should the amalgam faces of the rubbers be con- 
nected with the exterior coating of a Leyden jar, in the act of 
being charged, the effect would be much more satisfactory—the 
positive electricity of the coating neutralizing the negative of the 
rubbers. 
The first object having been thus obtained, it remains to pass 
to the second, viz. to obviate the injurious action of those parts of 
the rubber not in contact with the glass. For this purpose, it is 
plain that if a non-conducting substance be interposed between 
* Am. Jour. Sci. and Arts, Vol. xxiv, p. 256. t Franklin’s Letters. 
