672 Dr. ingenhousz’s Improvements 
I found the pafte-board disks not much lefs fufceptible 
of eleCtricity before 1 had varnifhed them than they 
were afterwards; but they loft their force again in a few 
minutes, and did not recover it till they were dried and. 
heated again. 
It is well known, that writing and brown packing pa- 
per, when warmed, may acquire a confiderable electrical 
power by being rubbed with hares skin, a piece of wood,, 
ivory, nay even (as I found by experience) with a metal- 
lic body. 
As it feems to be a general law of nature, that all refi- 
nous bodies, excited either with a pofitive or a negative 
electricity, are more tenacious of keeping it, or feem to 
part with it, as it were, with more reluctance than glafs 
(as I have demonftrated in a paper, read laft year before 
the Royal Society) ; it is advifeable, that the conductor of 
fuch a paper machine be not furnifhed with metallic 
points, which being neceffarily kept at a diftance will 
not take away all the eleCtricity ; but that fome flexible, 
conducting fubftance, as lilver or brafs lace fringes, com- 
municating with the conductor, be in clofe contaCt with 
the excited furface. 
As woollen cloth or Manchefter cotton velvet, and 
fuch like fubftances, excite a good deal of eleCtricity upon 
dried paper and refinous fubftances, and do not wear out 
fo 
