108 Hare’s Electrical Plate Machine. 
ameter should be less. The deficit caused in the hand in 
contact with the negative coating, is supplied by electricity 
from the arm; and this, again, from the body, where if the 
charge be inconsiderable, it is so much diffused as not to be 
perceived. In like manner, a slight surcharge received 
by the hand in contact with the positive coating, is diffused, 
as it proceeds up the arm to the chest, so as to be too fee- 
ble to be felt there. 0 
A piece of tin foil, interposed between paper, has been 
found not to be perforated by a charge, which had pierced 
the paper on both sides of it. 
1 were but one current, it is alleged that tin foil, 
situated as above mentioned, would be pierced during its 
passage from one coating to ihe other—a fortiori, then, it 
should be pierced, if two currents be necessary, passing 
each other. Besides, the explanation afforded, in the case 
ofa shock received by the hands, applies to this: owi 
to its great conducting power, the tin foil diffuses the 
attraction from each side, so much, as not to be dam- 
Art. XU1.— Description of an Electrical Plate Machine, the 
Plate mounted horizontally so as to show both negative and 
positive Electricity. Ilustrated by Engravings. By Ro- 
Bert Hare, M.D. Professor of Chemistry in the Univer- 
sity of Pennsylvania. . 
The power of electrical plate machines, has been gener- 
ally admitted to be greater, than that of machines with cyl- 
inders. The objection to the former has been, the difficul- 
ty of insulating the cushions, so as to display the negative 
‘ich, c r 
count, may not be unacceptable to the public.* 
*See Plate — Fig. 3% 
