394 Mr. cavallo's Experiments and 
ture, by the help, as ufual, of very diluted gum* water, 
I painted a card; but the electric fhock fent over this 
left not the lead: impreffion. 
Defirous of carrying this invefligation on colours a 
little farther, I procured fome pieces of paper painted on 
both fides with oil colours ^ and fending the charge of 
two feet of coated glafs over each of them, I obferved 
that the pieces of paper painted with lamp-black, Pruf- 
fian blue, vermillion, and purple brown, were torn by 
the explofion \ but white lead, Naples yellow, Englifh 
ochre, and verdigreafe, remained unhurt. 
The fame fhock lent over a piece of paper, painted 
very thick with lamp-black and oil, left not the leaft 
impreffion. I fent the fhock alfo over a piece of paper, 
unequally painted with purple-brown, and the paper was 
torn where the paint laid very thin, but remained un- 
hurt where the paint was evidently thicker. 
Having repeated thofe experiments feveral times, and 
with fome little variation, they were attended with dif- 
ferent effe<fts ; however, they all feem to point out the 
following proportion. 
I. A coat of oil-paint over any fubftance, defends it 
from the effects of fuch an electric fhock as would other- 
wife injure it; but by no means defends it from the force 
(c) The colours were mixed with linfeed oil. 
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