Metals. M I N E R 
which fmall cryftals of quartz-pyramids are covered with 
wood-like tin-ore ; from whence it fliould feem that the 
tin-ore was formed (ubfequent to the cryftals of quartz. 
This Hone is very rich in tin; it came from Gaverigan, 
in the parith of St. Columb. Fig. 6 is dark brown wood¬ 
like tin-ore, of a very folid texture, having different cir¬ 
cles of light-brown belts or veins, with hollow impreffions 
on the other tide, as if it had been formed on fmooth con¬ 
vex figures. Fig. 7 is very compact wood-like tin-ore, 
ihooting from hoilow centres, in oval or circular forms, 
and veins running from the centre to the circumference, 
with various (hades of brown. This is nearly as folid as 
agate. Fig. 8, 9, 10, 11, are feveral other varieties of 
wood-tin, or tooth-tin, ore ; thefe are more particularly 
called tooth-tin , from their form. 
Fig. is is an-ore of Saxon tin ; Knorr calls it “ a rich 
and noble fpecies.” It is of a dark red colour, with irre¬ 
gular cryftals in oppofite layers. The white facets are 
only plafterings of arfenic, which in the open air iffues 
from tire mat's, and adheres to the furface like meal. 
Fig. 13 is an ore of garnet-tin, fo called from its refem- 
blance to the garnets of Bohemia, in the mines of which 
country it chiefly occurs. It is dark red, fomewhat trans¬ 
parent ; form, a regular dodecahedron. Fig. 14 is a red- 
dith-brown tin-ore, at a, mixed with mica in a vein be¬ 
tween chlorite, h, or greenith peach mixed with mica, and 
a vein of quartz, c. From Carvath-mine, in the parith of 
St. Auftell, Cornwall. Fig. 15 is an ore of tin imbedded 
in tliorl; this fpecimen is of a greenith grey (haded with 
black. 
Fig. 16, 17. Cryftallized tin.—Fig. 16 reprefents a large, 
black, thining, tin-cryftal, with a very thort column and 
broad pyramid, which is interrupted by other cryftals 
forming thereon. This tin-ore is formed in a group of 
fmall cryftals of yellow topazes. It is a Angular fpecimen, 
and came from Trevaunance, in St. Agnes, Cornwall. 
Among the ores of tin we reckon thote exceedingly mi¬ 
nute cryftals which are hardly viiible in the ftone, but 
which, in proportion to fize, contain as much tin as the 
larger. Thefe cryftals, being imbedded in the ftone as in 
a matrix, but not being very firmly adherent, are eafy fe- 
parated from the matrix by fubterranean waters, or by 
the decompofition of the ftone. It is then called J'and of 
tin; fome of which is thown at fig. 17, in a box. 
Plumbum, Lead.—Generic chara&ers: Bluith-white, 
gradually blackening in the air; foft, very malleable, a 
little duftile and tenacious, not lbnorous, ftaining the 
fingers of a bluifh colour; fpecific gravity, eafily 
melting, exhibiting iridefcent colours on the furface dur¬ 
ing liquefaftion, and becoming firft a white, then a grey, 
then a yellow, and laftly a red, oxyd, all of which are 
eafily convertible into glafs foluble in all acids, and 
giving the tolution afweetitli tafte, precipitating a yellow 
powder if diflolved in nitric acid and potafli be added to 
the folution. 
Under the article Chemistry, vol. iv. p. 295-7, we 
have defcribed molt of the properties and the different 
preparations of lead, as far as we are acquainted with 
them. In Memoirs of the National Inftitute of France, 
vol. x. 1811. there is a paper by M. Guyton Morveau, 
which difclofes two fads refpebting lead, both of which 
appear to be anomalous. 1. That lead becomes of iefs 
fpecific gravity, when it is hardened by hammering or by 
being drawn into wires. 2. That diftilled water afts more 
readily on this metal than common river-water. The in- 
creafe of denfity in lead, by the procefs of hardening, 
teems to have been originally noticed by Muffchenbroeck; 
but was Amply ftated as a fad, wdthout any attempt at 
explanation. The firft objefl of the prefent author was 
to verify it, and to examine it under all its different rela¬ 
tions. Having obtained fpecimens of very pure lead, he 
lubje&ed them to blows of the hammer, and examined 
the efteft which was produced ; he then palled the lead 
through a rolling-prefs, and afterward had it drawn into 
Vol. XV. No. 1060. 
A L O G Y. Metals. 501 
wire, and alfo ftrongly comprefled by a ftamp, while in- 
clofed in a die. When the lead was fubmitted to ftrong 
preffure, but fo confined that its bulk was not increafed, 
the fpecific gravity was augmented, as is the cafe with the’ 
other metals. It was in the courfe of thefe experiments 
that the author was induced to notice the aftion of dif¬ 
tilled water on lead ; which a&ion, he obferved, was not 
exercifed when common fpring or river water was em¬ 
ployed ; and it was found to depend on fmall portions of 
lbine of the neutral falts that exift in this latter fluid. 
The fubftance formed appears to be an hydrat of lead! 
There are twenty-three fpecies of combinations, of lead. 
x. Plumbum nativum, or native lead. The exiftence of 
native lead has not yet been fatisfaftorily afcertained; 
and its ores are fo eafily reduced, and have been fo com¬ 
monly worked in all ages, that great caution would be 
requifite in examining local, circumftances, in order to 
determine whether a fpecimen, fuppofed to be native, 
were really fo, or only a portion of an ore that had been 
fmelted at fome former period. Particles of metallic lead 
have been found in a porous lava of the ifland of Madeira; 
but the peculiarity of their fituation may ferve to explain 
their pretence. Some affirm that native lead occurs in 
Monmouththire, Poland, and Silefia. 
2. Plumbum ochraceum, lead ore, or ochre : pulveru¬ 
lent ; without luftre, totally foluble in nitric acid with 
effervefcence, eafily reducible to a metallic ftate on char¬ 
coal. Found in the various lead-mines of Great Britain, 
Saxony, Germany, &c. in a loofe earthy ftate, and gene¬ 
rally feated on galena: colour white, grey, red, or yeflow; 
it becomes red when expofed to a fufficient heat, and con¬ 
tains a conliderable portion of carbonic acid gas: it yields 
from 60 to 80 per cent, of lead. 
3. Plumbum terreum, or earthy lead-ore : indurated; 
without luftre, earthy internally, foluble in nitric acid 
with effervefcence. Found with the lalt, of which it teems 
only an indurated variety, in larger or lefs mafles inter¬ 
mixed with other ores and foffils, in various fliades of 
white, grey, blue, yellow, red, or brown. 
4. Plumbum micaceum, or thining lead-ore : greafy to 
the touch, lamellar, of a til very colour and luftre. Found 
in the mines of the Hartz-foreft; and confifts of nume¬ 
rous plates incumbent on each other. 
5. Plumbum vitreum, or glafs of lead: femi-tranfparent, 
brittle, of a glaffy texture and luftre, and common form. 
Found in Somerfetffiire, and the lead-hills in Scotland; 
in France, Saxony, Siberia, Hungary, &c. Colour white*, 
grey, or yellowiffi-green: texture conclioidal or iplintery: 
it does not eftervelce with nitric acid. 
6. Plumbum fpatofum, white-lead-ore, or carbonat of 
lead: thining externally and internally; foft, white, de¬ 
crepitating in the fire, effervefcing with acids, generally 
in the form of cryftals. Found in various parts of Great 
Britain and Ireland; in Burgundy, Auftria, Saxony, Hun¬ 
gary, See. rarely in a globular or cellular form, but moft 
commonly cryftallized in rectangular eight-fided prifrns 
with obtufe pyramids varioully truncated, or in tables of 
various forms. Colour (ilvery or pale white, with fome- 
times a filky luftre, or tinged with brown, greenith, or 
yellowiffi: texture lamellar or conchoidal, of the cryftals 
often fibrous. It is foft enough to be cut with a knife, 
and is foluble in fat oils. When heated, it decrepitates; 
then turns yellow, and afterwards red: before the blow¬ 
pipe it is quickly reduced, and blackens with fulphurated 
volatile alkali. Specific gravity, from 6-25 to 6-93. Con¬ 
tains oxyd of lead 82, carbonic acid 16/ Klaproth. 
Many natural cryftals of this fubftance are of a black 
colour, owing perhaps to a change (imilar to that which 
takes place in confequence of the a&ion of alkaline ful- 
phurets : the colour in thefe inftances is only fuperficial. 
It has the double refractory power to a high degree; and 
the double image of an objeCt viewed through it is accom¬ 
panied with an iridefcent appearance, owing to the dif- 
perfion of the rays of light. This died: is often obferv- 
1M able 
