COPPER. 
50; 
roasting before it can be fluxed into copper. The 
force of the fire dissipates some of the vitriolic acid; 
what remains attacks and dissolves such a quantity 
of copper, that the water in which the roasted ore 
is washed (by means of old iron immersed in it ac- 
cording to the German method) produces great 
quantities of fine copper, so that the proprietors 
have there obtained in one year near one hundred 
tons of the copper precipitated from this water. 
The bishop of LandafF, to whom we are chiefly 
indebted for this information, adds, that if this 
water was afterwards evaporated, it would yield 
green vitriol, or vitriolated iron, at nearly the rate 
of two hundred tons of vitriol for each hundred ton 
of iron at least ; which, at the rate of three pounds 
sterling per ton, might perhaps produce very good 
profit to the undertakers, if any should settle such a 
manufacture there. 
Among the most considerable mines of this metal 
which are to be found in the different parts of the 
world, may be ranked those of Cornwall, between 
Hale and Rudworth, which are situated in a regular 
line along the bottom of the north side of a ridge of 
granite nills. The veins of mineral run parallel to 
each other; some of them are four or five feet 
thick, and are worked to the depth of three or four 
hundred feet below the surface of the earth. The 
ore produced mostly consists of yellow or pyritous 
copper, though native copper is also found in the 
mines ; and it is not a little singular, that this, of 
all other kinds the richest, should always be met 
