32.4 -A-//', mudge on the Conjlrn&ion 
though in this method of working I could give an ex- 
quilite poliih, as the putty lodged itfelf in the pitch 
exceedingly well, yet the figure of the metal was injured 
in the middle, nor did indeed the work go on with that 
equability which is the infeparable attendant on a good 
figure. In order to obviate this difficulty, I call fome 
metals with a continued face, the holes not going quite 
through, within perhaps the thicknefs of a fix-pence. 
I finiffied two or three metals of this fort, and the work 
promifed and went on very well ; but when I came to open 
the holes, which I did with the utmoft caution, I found 
the metals ffiort of perfection ; which I attributed to an 
alteration of the figure from the removal of even that fmall 
portion of metal after the fpeculum had been finiffied. 
.This I do fuppofe was in fome meafure the reafon why I 
fpoiled a very diftinCt and perfect two-foot metal, which 
bore a charge of two hundred times, only by opening 
the fharp part of the edge of the hole, becaufe I thought 
it bounded the field : fo eflentially neceffary is an exqui- 
fite correCtnefs of figure in the fpeculum of a pcrfeCt 
refiebtor. 
This experiment not fucceeding, inftead of calling the 
metal without a hole, I made one quite through the 
middle of the poliffier, a little lefs than that in the Ipe- 
culum. This perfectly anfwered the purpofe; no more 
incon- 
