[ 19 ] 
brown-coloured cloud, with a precipitate of the fame 
colour. 
A {Hilling and a (ixpence, put into two different 
tea-cups, were prefently tarnilhed, and became of a 
very dark colour. 
Each drop of a folution of filver in fpirit of nitre, 
occafioned a dark brown or blackifh cloud, and fell 
in form of a black precipitate to the bottom of the 
glafs. 
Some very white faccharum faturni turned imme- 
diately black, and precipitated in form of a black 
powder to the bottom of the glafs. 
Four pounds feven ounces and fix drachms, (or 
lxxi ounces vi drachms) were poured into a (lone 
bafon, which was put on a land heat to evaporate 
with a flow fire. 
As foon as the water became warm, it loft its 
ftrong fulphureous fmell, and there appeared fome 
flakes of a dark brown light earth, which dropt to 
the bottom. After about one half was evaporated, 
a very thin pellicle was oblerved on the furface, 
which precipitated to the bottom, and when it was 
reduced to about a pint ( lib. i. ), it was filtrated 
through paper, and about 2 J gr. of a dark grey 
infipid fediment was feparated. This fediment 
was compofed of the dark coloured earthy flakes, 
which were obferved fo foon as the water had become 
warm, and of a fmall quantity of a whitifh, infipid 
gritty matter, which had formed the very fine thin 
pellicle. Some of it being throw’n into diftilled wa- 
ter, and oil of vitriol dropt into it, an effervef- 
cence enfued, and the black earthy part diffolved, 
though the reff remained infoluble ; hence the firft 
D 2 part, 
