OF CORNWALL. i 35 
The three forts of mundic above-mentioned, Section vii, differ sect. xiv. 
not only in colour, but in the more decifive and lefs variable pro- Weight of 
perty, weight. mundic. 
f Plate-mundic ftriated weighed to water (Au- 
) guft 19 r 755) as - - - - - - 
i Plate-mundic granulated - - - - - 
to 1. 
r Brafs-coloured cubical mundic 
lD°. - - - granulated - 
f Brown-mundic - - - - 
1 Second fample of D°. 
to 1. 
to 1. 
The plate-mundic therefore is in weight to water near as feven to 
one ; the brafs-coloured is not fo heavy, being but as five to one ; 
and the brown is ftill lighter, being but as 4 - - ’to one. 
Notwithftanding that the fpecifical weight of mundic exceeds sect. xv. 
that of moft follils, and that it has, to all outward appearance of l ts produce, 
colour and texture, fuch a near refemblance to brafs, it is fo preg- 
nant with fulphur and arfenick, that, though a fierce fire will melt 
it, yet will it fly into powder under the hammer, and by no flux 
hitherto difeovered can it be reduced into a metal. Notwithftand- 
ing the failure of all former experiments, the appearance promifed 
fo much, that the late learned Dr. Boerhave lent to me by a friend m 
for all the forts of it which could be procured, in ftrong confidence 
that he fhould be able to find out a method of making it turn to 
account. All the forts were accordingly furthered to him ; but the 
death of that great chemift foon after, deprived us of thofe aflidu- 
ous and fkilful experiments, which, under his eye, might have been 
bleifed with difeoveries of great importance. 
Mundic will yield in evaporation its. quantity of fulphur and 
arfenick ; but thefe are fo much eafier, and at a left expence, to be 
procured other ways, that it is not worth while to endeavour after 
them by burning mundic. Mr. Boyle " procured by diftillation four 
ounces of good brimftone from three pounds of thefe ftones ; and 
fays, that they contain particles of copper and iron ; that mercury 
may be thence procured ; and that a fkilful perfon may poftibly 
make a profitable ufe of marcafites, either by fixing the volatile 
gold or filver contained therein, or by graduating filver by their 
means ; and Kentmannus obferves, that fome marcafites contain 
filver, others gold, and others both, ibid. The white or plate- 
mundic far exceeds the other forts in weight ; and, if I am not 
n Boerh, Theor. of Chemiftry, Englifh. 
mif- 
Dr. J. Andrew of Exeter, then at Leyden. 
