MINE. 
or horizontal fissures'. This, by the Cornish 
tinners, is called a door or squat ; which, 
properly speaking, is a hole or chasm im- 
pregnated with metal, making no continued 
line of direction or regular wails. Neither 
does a floor of ore descend to any consider- 
able depth ; for underneath it there appears 
no sign of a vein or fissure, either leading di- 
rectly down,' or any ether way. This kind 
©f vein is very rare in Britain. The fissures 
most common in Britain are the perpendicu- 
lar and inclined, whether their direction is 
north or south, east or west. 
The perpendicular and horizontal fissures 
probably remain little altered from their first 
position, when they were formed at the indu- 
ration of the strata immediately after the wa- 
ters left the land. The perpendicular fissures 
are found more commonly situated in level 
ground, at a distance from hills, and from the 
sea-shore ; but with regard to the latter, we 
find that the upper and under masses of strata 
differ in their solidity and other properties. 
Hence it is very plain that inclined fis- 
sures owe their dellection or underlie to some 
secondary cause, violence, or subsidence of 
the earth ; for though perpendicular fissures 
are seldom to be seen, yet such as are in- 
clined at very considerable depths become 
more and more perpendicular, as the more 
central strata, from the vast superincumbent 
weight, do not seem so likely to be driven 
out of their position as those which lie nearer 
the surface.” 
The fissures- are often met with fractured 
as well as inclined ; the reason of which has 
probably been a subsidence of the earth from 
some extraordinary cause. Though the me- 
tallic veins generally run from east to west, 
they are frequently intersected by veins or 
lodes of other matters, which run from north 
to south. Some of these cross veins contain 
lead oi antimony, but never tin or copper. 
Sometimes one of these unmetallic veins in- 
tersects the true one at right angles ; some- 
times obi quel y ; and sometimes the mixture 
of both is so intimate, that the most expert 
miners are at a loss to discover the separated 
part of a true vein. When this last is inter- 
cepted at right angles, it is moved, either 
north or south, a very little way, perhaps not 
more than one fathom ; in which case the 
miners having worked to a small distance in 
one of these directions, if they find themselves 
disappointed, turn to the other hand, and sel- 
dom fail of meeting with what they expected. 
Sometimes they are directed in their search 
by the pointing of a rib or string of the true 
vein; but when the interruption happens in 
an oblique direction, the difficulty of finding 
the vein again is much greater. 
When two metallic veins in the neighbour- 
hood of each other run in an oblique direc- 
tion, and of consequence meet together, they 
eommmonly produce a body of ore at the 
place where they intersect ; and if both are 
rich, the quantity will ire considerable ; but 
if one is poor and the otheV rich, then both 
are either enriched or impoverished by the 
meeting. After some time they separate 
again, and each will continue its former di- 
rection near to the other ; but sometimes, 
though rarely, they continue united. 
It is a sign of a poor vein when it separates 
©r diverges into strings ; but, on the con- 
trary, when several of them are found rurtning 
into one, it is accounted a promising sign. 
Sometimes there are branches without the 
walls of the vein in the adjacent strata, which 
often come either obliquely or transversely 
into it. If these branches are impregnated 
with ore, or if they underlie faster than the 
true vein (that is, if they dip deeper into the 
ground), then they are said to overtake or 
come into the lode, and to enrich it ; or if 
they do not, then they are said to go off from 
it, and to impoverish it. But neither these, 
nor any other, marks, either of the richness 
or poverty of a mine, are entirely to be de- 
pended upon : for many mines, which have a 
very bad appearance at first, do nevertheless 
turn out extremely well afterwards ; while 
others, which in the beginning seemed very- 
rich, turn gradually worse and worse : but, 
in general, where a vein has had a bad ap- 
pearance at first, it will be imprudent to be 
at much ex pence with it. 
Veins of metal, as has been already ob- 
served, are frequently so compressed betwixt 
hard strata that they are not an inch wide ; 
nevertheless, if they have a string of good 
ore, it will generally be worth while to pur- 
sue them; and they frequently turn out well 
at last, after they have come into softer 
ground. In like manner, it is an encourage- 
ment to go on if the branches or leaders of ore 
enlarge either in width or depth as they are 
worked ; but it is a bad sign it they continue 
horizontal without inclining downwards ; 
though it is not proper always to discontinue 
the working of a vein which has an unfavour- 
able aspect at first. Veins of tin are worth 
working when only three inches wide, pro- 
vided the ore is good ; and copper ores when 
six inches wide will pay very well for the 
working. Some of the great mines, how- 
ever, have very large veins, with a number 
of other small ones very near each other. 
There are also veins crossing one another 
sometimes met with, which are called contras, 
vulgarly caunters. Sometimes two veins run 
down into the ground in such a manner that 
they meet in the direction of their depth ; in 
which case the same observations apply to 
them as are applicable to those that meet 
in an horizontal direction. Sometimes a vein 
will suddenly disappear without giving any 
warning, by becoming narrower, or of worse 
quality ; which by the miners is called a start 
or leap, and is very common in the mines of 
Cornwall. In one day’s time they may thus 
be disappointed in the working a rich vein of 
tin, and have no further sign of any thing to 
work upon: at the fractured extremity of 
their vein they perceive a body \of clay or 
other matter ; and the method of recovering 
their vein is to drive on their work in the di- 
rection of the former part, so that their new 
work shall make the same angle with the clay 
that the other part of the vein does. Some- 
times they sink a shaft down from the sur- 
face ; but it is generally a matter of difficulty 
to recover a vein when thus lost. 
The method of discovering mines is a 
matter of so much difficulty, that it seems 
surprising how those who were totally unac- 
quainted with the nature of metals first came 
to think of digging them out of the earth. 
In modern times we know that mines have 
been frequently discovered by accident ; as 
in sea-cliffs, among broken craggy rocks, by 
the washing of the tides or floods ; also by 
irruptions and torrents of water issuing out of 
19 § 
hills and mountains, and sometimes by the 
wearing of high roads. 
Mines, however, are now most commonly 
discovered by investigating the nature of 
such veins, ores, and stones, as may seem 
most likely to turn to account : but there is a 
particular sagacity, or habit of judging irom 
particular signs, which can be acquired only 
by long practice. Mines, especially those of 
copper, may also be discovered by the harsh 
and disagreeable taste of the waters which 
issue from them ; though it is probable that 
this only happens when the ore iies above the 
level of the water which breaks out ; for it 
does not seem likely that the taste of the ore 
could ascend, unless we were to suppose a 
pond or lake of water standing above it. 1 lie 
presence of copper in any water is easily dis- 
covered by immerging in it a bit ot polished 
iron, which will thus instantly be turned of a 
copper colour, from the precipitation ol the 
metal upon it. A candle, or a piece of tallow, 
put into water of this kind, will in a short 
time be tinged of a green colour. 
After the mine is found, the next thing to 
be considered is, whether it may be dug to 
advantage. In order to determine this, we 
are duly to weigh the nature ot the place, 
and its situation, as to wood, water, carriage, 
healthiness, and the like ; and compare the 
result with the richness of the ore, the charge 
of digging, stamping, washing, and smelting. 
The form and situation of the spot should 
be particularly well considered. A mine 
must either happen, 1. in a mountain; 2.- 
in a hill; 3. in a valley ; or, 4. in a fiat. Bub 
mountains and hills are dug with much 
greater ease and convenience, chiefly because- 
the drains and burrows, that is, tire adits or 
avenues, may be here readily cut, both to 
drain the water, and to form gangways for 
bringing out the lead; Ac. In all the four 
cases, we are to look out for the veins which 
the rains or other accidental circumstances 
may have laid bare ; and it such a vein is 
found, it may often be proper to open the 
mine at that place, especially if the vein, 
proves tolerably large and rich : otherwise 
the most commodious place for situation is 
to be chosen for the purpose, viz. neither on 
a fiat, nor on the top of mountains, but on 
the sides. T he best situation for a mine 
is a mountainous, woody, wholesome spot 
of a safe easy ascent, and bordering o^ a na- 
vigable river. The places abounding with 
mines are generally healthy, as standing 
high, and everywhere exposed to the air; 
yet some places* where mines are found prove 
poisonous, and can upon no account be dug. 
Devonshire and Cornwall, where there are 
a great many mines of copper and tin, are a 
very mountainous country, which gives an 
opportunity in many places to make adits or 
subterraneous drains to some valley at a dis- 
tance, by which to carry off the water from 
the mine, which otherwise would drown 
them out from getting the oi e. These adits 
are sometimes carried a mile or two, and dug 
at a vast expence, as from 2000/. to 4000/. 
especially where the ground is reeky ; and 
yet they find this cheaper than to draw up the 
water out of the mine quite to the top, when 
the water runs in plenty, and the mine is 
deep. Sometimes, indeed, they cannot find 
a level near enough to which an adit may be 
carried from the very bottom of the mine 
yet they find it worth while to make an add 
