The Artist's Assistant, In the Study and Practice of Mechanical Sciences: Calculated for the Improvement of Genius. Illustrated with Copper-Plates (Birmingham, [ca. 1785])

THE ARTIST'S ASSISTANT. 45

colour extremely well. It may be prepared in great
perfection by the following procefs.

£; Take of quickfilver eighteen pounds, of flowers
" of fulphur fix pounds : melt the fulphur in an
c: earthen pot ; and pour in the quickfilver gradual-
t: ly, being alfo gently warmed; and ftir them weil
£: together, with the fmall end of a tobacco-pipe.
': But, if from the effervefcence, on adding the latter
<: quantities of the quickfilver, they take fire, extin-
" guifh it by throwing a wet cloth (which fhould be
t! had ready) over the veflel. When the mafs is cold,
" powder it, fo that the feveral parts may be well
" mixed together. But it is not neceffarv to reduce
£: it, by nicer levigation. to an impalpable (late.
t: Having then prepared an oblong glafs body, or
£: fublimer, by coating it well with fire-lute over
': the whole furface of the glafs, and working
" a proper rim of the fame round it, by which it
u may be hung in the furnace in fuch a manner that
" one half of it may be expofed to the fire, fix it in
a proper furnace, and let the powdered mafs be
u put into it, fo as to nearly fill the part that is
M within the furnace ;. a piece of broken tile being
" laid over the mouth of the glafs. Sublime then
i: the contents, with as ftrong a heat as may be ufed
" without blowing the fumes of the vermillion out
M of the mouth of the fublimer. When the fublima-
" tion is over, which may be perceived by the
<! abatement of the heat towards the top of the body,
£; difcontinue the fire ; and, after the body is cold,
t; take it out of the furnace, and break it : collect
£; then together all the parts of the fublimed cake,
" feparating carefully from them any drofs that may
4i have been left at the bottom of the body, as alfo

any