of Metals for reflecting ti defcopes. 323 
and this is ordinarily fufficient to give a general figure to 
the furface of the pitch. The bruifer and polifher. are 
then fuffered to grow perfectly cold, when the pitch, 
conlidering what has "been taken off, will be about the 
thicknefs of a fliilling. 
It is however here neceffary to obferve, that the pitch 
Ihould be neither very hard and refinous, nor too foft; if 
the former, it will be fo untraftable as not to work 
kindly ; and if too foft, it will in working alter its figure 
falter than the metal, and too readily fit iilelf to the ir- 
regularity of . its figure, if it have any. When both tools 
were perfectly cold, I gave the polifher a gentle warmth, 
and then fixed the bruifer to the block with its face up- 
wards; and (having with a large camel’s-hair brufh 
fpread over the face of the poliiher a little water and foap, 
to prevent flicking) with fhort, ftraight, and round 
ftrokes I worked it upon the bruifer, every now and then 
adding a little more water and foap, till the pitch upon 
the polifher had a fine furface, and the true form of the 
bruifer; and this I continued to do till they both grew 
perfectly cold together : in this manner the poliiher was 
perfectly formed in about a quarter of an hour. But 
here a difficulty arofe : when I begun to polilh the metal, 
I found that the edge of the hole in the metal collected 
the pitch towards the middle of the polifher; and 
T t 2 though 
O 
