of Metals for reflecting Telefcopes. 313 
and metal muft be like wife cleared in the fame manner, 
and with equal care, from any lurking particles of emery. 
The hones being fixed down to the block, you now 
begin to work the bruifer upon them with very cautious, 
regular, fhort ftrokes, forward and backward, to the 
right and left, turning the axis of the bruifer in the hand 
while you move round the hones, by fluffing your pofi- 
tion, and walking round the block. Indeed the whole 
now depends upon a knack in working, which fhould be 
conduced nearly in the following manner. Having 
placed the bruifer on the centre of the hones, Hide it in 
an equable manner forward and backward, with a ftroke 
or two diredtly acrofs the diameter, a little on one fide, 
and fo on the other; then fluffing your pofition an eighth 
part round the block, and having turned the bruifer 
in your hand about as much, give it a ftroke or two 
round and round, but not far over the edges of the hones, 
and then repeat the crofs ftrokes as before : thofe round 
ftrokes (which ought not to be above two or three at 
moft) are given every time you ftiift your own pofition 
and that of the metals, previous to the crofs ones, in 
order to take out any ftripes either in the hones or 
bruifer, which may be fuppofed to be occafioned, by the 
ftraight crofs ftrokes. During the time of working, no 
mud muft be fuffered to colledt upon the hones, fo as to 
Vol. LXVII. Sf deftroy 
