[ 4 § ] 
heat of the fire, or paffing the brufh over them. I 
then rubbed it with a foft linen cloth, and thereby 
procured a kind of glofs, which I afterwards in- 
creafed by rubbing it with an hard brufh j which 
was fo far from fcratching or leaving any marks on 
the picture, that it became more fmooth and polifhed 
by it. 
After I had made all the foregoing experiments, in 
converfation with my honoured and learned friend 
Dr. Kidby, a fellow of this Society, I faid I had 
been trying to find out what the encauftic painting 
of the ancients was. Upon which, he told me, that 
there was a paffage in Vitruvius de architeclura rela- 
tive to that kind of painting ; and was fo good as to 
tranfcribe it for me from the 7th book, chap. 9. De 
minii temperaturci. Vitruvius’s words arej Jt jiquis 
fubtilior fuerit , & voluerit expolitionem miniaceam 
j'uum colorem retinere , cum paries expolitus & aridus 
fuerit 7 tunc ceram punicam liquefadiam igni , paulo 
oleo temperatam 3 feta inducat 3 delude poflea carboni- 
bus inferreo vaje compoftis , earn ceram apprime cum 
pariete , calefaciendo J'udare cogat , fiatque ut perce- 
quetur 3 deinde cum candela linteifque puris Jubigat y 
uti figna marmorea nuda curantur. Htec autem 
xctvais grace dicitur. lta ob/lans ceree punica lorica 
non patitur , nec lunce fplendorem 3 nec foils radios lam- 
bendo eripere ex bis politionibus colorem. 
Which I thus tranflate : “ But if any one is more 
<f wary, and would have the polifhing [painting] 
with vermilion hold its colour, when the wall is 
painted and dry, let him take Carthaginian [Bar- 
lt bary] wax, melted with a little oil, and rub it on 
<{ the wall with an hair pencil j and afterwards let 
“ him 
