OF CORNWALL. mt 
Lead is fometimes found fo involved and hidden in fpar, that) 
were it not for its eminent weight, no metal would be fufpeded. 
Some of this Ipar is like a pumice-ftone s , fome granulated, others of 
a fibrous ftriated texture, like the fplinters of a bone glewed toge- 
ther, and of a brownifh colour h ; fome of a tabulated cryftal, making 
little or no effervefcence with aqua forth , of a whitifii ochrous co- 
lour, tranfparent ' ; another fort of white tranfparent fpar in ftraight- 
lined columnar ftrice , from Cardiganfhire in Wales, of which we have 
fome alfo in England. Some ores of this metal are cavernous, in green 
cryftals, which are fcarce : at Mifnia, in Germany, it is found in 
beautiful colours, in Mendip hills Somerfetfbire, in Denbighfhire, 
and at Penros in Cornwall \ Of like fort, but in a more ochrous 
feeder, I have feen lead-ore broke in the tenement of Nanikeg, in 
Illogan parifli, bedded in a yellow clay of the exad colour of ful- 
phur, without any other fulphureous fign but that of colour, very 
heavy, and reckoned rich in lead. This laft ore is variegated in 
St. Iffy works, Cornwall *. We have alfo in Cornwall a foliaceous 
talky kind of lead-ore, but what I have feen is light in comparifon, 
and of lefs beauty than the ftriated talky lead-ore from Ireland, 
which is white, fpeckled with purple, and exhibits very elegant 
fpecimens. Lead is feldom, fome think never found in a native, that 
is, in a metallic ftate ; but Dr. Woodward m has given us an account 
of one fpecimen of this kind, and Linnaeus has native lead found 
in Germany, which he calls Plumbum nudum (Syft. Nat. page 184, 
N°. I.) Lead is alfo faid to be found compleat and malleable in 
a mine of the ifiand Jamaica. It is however very fcarce, and in 
general, if lead-ore will yield three parts in four of the metal, {viz. 
feventy-five out of one hundred) it is reckoned very rich, but if 
it yields only forty out of one hundred, it is not worth working, 
unlefs eafy to come at. Lead-ore may be very rich in lead, and yet 
not afford one grain of filver ; and, on the other hand, the ore which, 
is poor in lead, does fometimes yield filver plentifully. As to the 
potter’s ore, the finaller the grains the more filver they are likely to 
contain, and vice verfd n ; but where-ever filver is found incorporated 
with lead, extrading the filver does by no means impoveri£h it ; 
if the aflay be Ikilfully performed, it leaves the lead in a better and 
more ufeful ftate than it was before 0 ; but lead is very apt to con- 
fume and lofe of its weight every time it is melted ; upon this, and 
many other accounts therefore, it requires a ikilful hand to make 
the moft of it. 
£ From Turky. 
h From Tipperary, in Ireland. 
1 From Ireland. 
k See Woodward’s Cat. vol. II. page 28. 
1 Ibid. vol. I. page 217. 
m Ibid. vol. II. page 28, 1 . 23. 
* Grew’s Muf. R. S. page 329. 
0 Sir Hum. Mack worth, page 41. 
Our 
