' of Metals for reflecting I’elefcopes. 325 
inconvenience arofe from the gathering of the pitch (for 
it had now no greater tendency to collect at the center 
than the tides) and I finilhed feveral metals fucceffivelv, 
excellent both in point of figure and polifh ; one of thole 
of two inches diameter and 7,5 focal length, bore a charge 
of fixty times. and upwards, which when mounted in a 
telefcope I gave to my brother. This telefcope underwent 
Mr. short’s examination, who was pleafed to remark 
only, that he thought he had made one more diftindt. 
I mult obferve, that in this method of working the 
polilhing goes on in an agreeable, uniform, and fmooth 
manner; and that the fmall degree of yielding in the 
pitch (which is actually not more than the wearing of 
the metal) produces that mutual accommodation of 
furfaces fo neceffary to a true figure. In the beginning 
of the polifh, and indeed for fome time during the pro- 
grefs of it (always remembering now and then to move 
the metal round its axis) I worked round and round, not 
far from and always equally diftant from the center, ex- 
cept that every time, previous to the drifting the metal 
on its axis, I ufed a crofs ftroke or two ; and when the 
polifh was nearly compleated, I moftly ufed crofs ftrokes, 
giving a round ftroke or two likewife every time I turned 
the metal on its axis. I oblerved in this method of work- 
ing, that the metal always polilhed fafteft in the middle; 
info much, 
