284 Copper Mines. 
or other hard substance, in which the minerals are em- 
bedded, and which varies in proportion to the density of 
such surrounding matter, Sometimes, a miner considers 
himself remunerated by working at Ios. per fathom, or six 
feet, or even less, whilst the almost incredible sum of £400 
has been known to be paid for working through an exceed- 
ingly hard stone the same distance; and it is obvious, that, 
unless the substance surrounding the ore be occasionally re- 
moved, the operations in the mine could not be prolonged, 
because the ore would not continue within reach. And it 
not unfrequently happens, that, prior to the abandonment 
of a mine, or where the labourers are paid not in proportion 
to their labour, but in proportion to the quantity of ore 
they extract, this is actually the case. Succeeding adven- 
turers have then the unprofitable work of extracting stone, 
at a great outlay before such mine can be again rendered 
in a proper working condition. 
In mining districts, the existence of copper is often pre- 
sumed from some accidental circumstance; such, as when 
in the digging of a trench, or the removing of stone, some 
fragment is observed to exhibit verdigris or other coppery 
indication, generally very slightly, but enough to stimulate 
an adventurous person to pursue it. In some places, the 
same mineral is denoted by a green appearance on the 
surface of rock or stone, sufficient to tempt a partial exca- 
vation by way of experiment. But indications, though oc- 
casionally very extensive, are not unfrequently very delu- 
sive ; for a small portion of bland oxide of copper is capable 
of tinging a large surface of ground. 
Symptoms of copper often occur in situations ill-adapted 
for experiment, such as the middle of a perpendicular cliff, 
or on the sea-shore, near low water mark. In such event, 
it is usual to examine the ground attentively, eastward or 
westward, with a view of finding some other indication in 
the direction in which the vein may be supposed to run. 
If such indication should be met with, it will be, probably, in 
a situation where the same objection would not be offered 
against excavating, in which case, a shaft is sunk accord- 
ingly and, if no such indication should occur, it is then the 
usual practice to fix upon some spot which appears most 
eligible in point of locality, and (as far as supposition can 
go), upon the same stratum for the sinking of a shaft by 
way of experiment. All these points are left to the discre- 
tion of the person to whom the mining operations are con- 
fided, and who is called a captain ; of which species of 
