19 8 Arbor Veneris, or, the Copper c Cree, 
the fame Shop at different Times % : which 
is the Reafon 1 could never exactly afcertaiii 
by Weight the juft Proportion of the Mer ~ 
cury ana Salt '-Ammoniac •, that depending 
on the Strength and Competition of the 
Aqua Forth, and therefore will admit of no 
other Rule than observing the Colour and 
Coniiftenqe of the Mixture, which if not 
white enough wants Mercury, and if too 
thin wants Salt Ammoniac, or both. But 
as neither of thefe mull; be in Quantity to 
weaken much the Solution of Copper, his 
advifeable to ftir them in by a very little at 
a Time. As much' of the Solution of Mer¬ 
cury As may amount to ^bqut W Part of the 
Whole, and four or five Grains of Salt Am¬ 
moniac to half an Ounce of Aqua Fortis, is 
ufually near the Mark. If right, after hand¬ 
ing a little, a thick white creamy Matter 
riles to the Top, a white Sediment falls to 
the Bottom, and the Middle is a fine trans¬ 
parent blue Ijjc[uQr„ When lift'd it muft be 
ftirred together, and employed before it fepa- 
rates : and when fpread upon the Glafs it ap¬ 
pears of a bleuifh whitewhich Ground is 
* Some Aqua Forth I bought became in diffolving pop¬ 
per not of a blue but of a green Colour; but on putting ia 
the Mercury it changed to a molt lovely blue, and made the 
heft Mixture I ever had ; for it might be, feen to vegetate in 
a Minute’s Time: and produced, in a few Hpurs, vigorous 
Branches of an Inch in Length. But there is fome Nicety re- 
quiftte in the Management of the Mercury ; for the Minute 
it is diffolved by the Aqua Forth, even before the Fermenta¬ 
tion is quite over, it muft be mixed with the Solution of Cop¬ 
per, or elfe it will concrete into a white Subftance like Salt, 
ami never mix intimately with the Copper Solution*, 
• ■ " 6 fb 
