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])

52 THE ARTIST'S ASSISTANT.

'; pear to produce any ebullition in the aqu >:"
'; and, having (trained off this folution through
'; flannel, pour it into the other by degrees ; obierv-
" ing whether it produce any effervelcence on put-
': ting in the la ft quantity : which if it do in any
': great degree, more of the cuttle-fifh-bone muft be
<: diffolved in aquafortis : and the folution very gra-
': dually added till no ebullition appear to be railed
" by it in the mixture. If this be properly ma-
': naged, the fluid will foon become clear and co-
'; lourlefs, and the tinging particles extracted from
'; the fhreds, together with the cuttle-hfh-bone,
ei will fubfide to the bottom and form a crimfon
': lediment; which is the lake. The water muft
': then be poured off: and two gallons of hard
" fpring water muft be prit to the lake, and well
'; ftirred about to mix them. This being likewife

poured off, after the lake has again fettled to the
f* bottom, muft be replaced by another two gal-
'; Ions; and the fame method muft be repeated four
': or five times. But if hard water cannot be pro-
" cured, or the lake appear too purple, half an
" ounce of alum fhould be added to each quantity
ff of water before it be ufed. When the lake is thus
Ci fufficiently freed from the falls, it mult have the.
ff water drained from it in a filter covered with a
t; linen cloth, which has been fo worn as to have no
<J nap or down remaining on its furface. After the
%: lake has been drained to a proper drynefs, it muft

be dropped on clean boards, by means of a proper
t; funnel : through which, the drops being fu.fferecl
c: to pafs, and reft on the board at proper diftances,
<; they will become fmall cones or pyramids; in
" which form the lake muft be buffered to dry, and
i: the preparation is then completed."

ROSE