C *96 3 
XVI. Directions for making the bejl Compojition for the 
Metals of reflecting Telef copes ; together with a Befcrip- 
tion of the Proce/s for grinding , polijhing , and giving 
the great Speculum the true parabolic Curve. By Mr. 
John Mudge; communicated by Alexander Aubert, 
Efq. F. R. S. • 
Read Feb. 27.^ March 6, and 13. Jk g t h e method of calling, 
■** grinding, and polifhing the 
fpecula of reflecting telefcopea, by MelT. molyneux and 
■Hadley, which is publdfhed in Dr. smith’s Optics, is 
what the workmen have generally followed, and is 
confequently well known to them ; I fhall in the follow- 
ing account avoid a repetition of the general directions 
there given,, and only remark upon fuch parts of that 
procefs which I think are efientially defective, and fup- 
ply them by a method of my own, which, from long 
and repeated trials, I have found completely to anfwer 
vthe purpofe. After, therefore, referring to the above 
account for the manner of making the gages, patterns, 
the method of calling, as well as a great many other par- 
ticulars, I will begin with 
Phe 
