666 Dr. ingenhousz’s Improvements 
The fame gentleman found glaffes, prepared in the 
above mentioned way, far fuperior in ftrength to a cake 
of rolin ufed in the eledtrophorus. He publifhed his me- 
thod in a pamphlet, intitled, Expofe d'une Met bode, par la 
quelle on rend les Difques de Ferre deftines a des Ma- 
chines EleSlriques capables d' exciter I'EleBricite dans une 
Air humide , fuivi d’une Maniere de faire de tres tons 
coujfms pour frotter les Ferres des Machines eleclriques, et 
•de la Defcription d'un Electrophone perpetuel plus parfait 
que ceux dont on s' eft fervi jufq' ici. A la Haye, 1778. 
Thofe who make ufe of plate machines fhould care- 
fully avoid putting the apparatus near the fire, for the 
purpofe of drying or warming it ; becaufe the fudden ex- 
panlion of the glafs by the heat cannot fo quickly pro- 
pagate itfelf through its whole extent ; for the center 
being commonly fqueezed between two flat fhives of 
brafs, with a piece of leather between the metal and the 
glafs, does not acquire a fimilar degree of heat at the 
fame time as the reft, and cannot fo eafily expand ; and 
therefore the plate is in great danger of breaking. If, in 
confequence of fuch a blunder, a flaw fhould happen, its 
progrefs might be flopped by drilling a round hole at 
the extremity of the flaw. Thefe flat glaffes may very 
fafely be rubbed with a dry warm cloth. 
As 
