f - df Metals for refl'eSling feTef copes. 3 2 1 
" 'Without enlarging, therefore, oh the difficulty 'of the 
; above "procefs, and the impoffibility of giving the fpecu- 
lum fhecorreCtnefs" and the' kind of figure "effentially 
neceffary toa- good telefcope, I will defcribe (by way of 
• iutrodudtion to the 'fucceeding' directions) tlie fteps by 
which I was led to a certain and e'afy method of giving a 
proper and correct parabolic figure to the metal, even 
though ; it cameoff imperfeCt from the hones, and an ex- 
quifite polifli at the fame - tim e . 
Having made many efforts in the former method, 
which by no means pleafed me for the reafons above-men- 
tioned; and having obferved, from feme of Mr. short’s 
telefcopes which fell into my hands, that the highliiftre of 
the polifli could never have been produced in the manner 
above- deferibed, but by fome fofter and more tender fub- 
ftance; and at the fame time recollecting, that Sir Isaac 
newton had given an account in his Optics of his hav- 
ing finifhed fome metals, and confiderably mended the 
objeCt glafs of a refraCtor, by working both upon a tool 
whofe furface had been covered with common pitch 
about the tMcknefs of a gfoat; reflecting, I fay, upon 
■ thefe matters (coarfe and uncertain as this method ap- 
peared at firft fight) 1 was determined to try whether I 
■ could not get rid of my embarraffment, by a mode of 
■ operation fomewhat fimilar. Accordingly, fhertening 
• Vol. LXVII. T t Dr. 
