The business of a mine is managed by a foreman, called the Captain, who keeps the accounts, and pays and regulates the miners; there are also Under-ground Captains, who have the immediate inspection of the works below. There exists a popular belief that the Cornish miner frequently lives under ground for many days, or weeks, without ever visiting the surface. This is never the case at any time, or under any circumstances. He does not even eat, much less sleep, in the mine, but returns to grass, and to his home, often many miles distant, at whatever depth he may have been working, when relieved from his labours.
With respect to the value of the mines, considered as property, it may be observed, that the whole concern is a Lottery, in which there exist many blanks to a prize, and were the whole of the speculation to be invested in any one individual, there is no doubt but that, after paying the required dues to the lords of the soil, and defraying the necessary expenses for working the mines, he would at the conclusion of the year be a loser by many thousand pounds. It is very true that there are many cases of extraordinary gain,[105] but these are balanced by more numerous concerns in which loss is incurred. How then does it happen that any capitalists can be induced to engage in the speculation? The answer is obvious, for the very same reason that they are induced to purchase tickets in the State Lottery. There are moreover additional motives which induce individuals of a certain description to embark in the speculation, although, as simple adventurers, they may scarcely anticipate success, such are landholders, who are naturally desirous of promoting an undertaking from which they must necessarily receive considerable dues; or merchants, who by becoming shareholders, are empowered to supply the mines with timber, candles,[106] gunpowder, and other articles which are required for its working.
Having thus considered the mode in which the ore is excavated from the mine, and brought to the surface, let us examine the processes which it ultimately assumes the state of marketable metal.
The Tin ore is first spalled, as it is termed, that is, broken into smaller fragments, and separated from the worthless parts; it is then pounded in the Stamping mill,[107] an operation which is essential to the complete separation of the oxide from the hard matrix through which it is disseminated: if full of slime it is first thrown into a pit called a buddle, where it is worked in order to render the Stamping more free, and to prevent it from choaking the grates; if however it is free from slime, the ore is shoveled into a kind of sloping canal of timber, called the Pass, whence it slides by its own, weight, and the assistance of a small stream of water, into the box where the Lifters work; the Lifters are raised by a water wheel, and they are armed at the bottom with large masses of iron weighing nearly two hundred weight, which pound or stamp the ore small enough for its passage through the holes of an iron grate fixed in one end of the box, a rill of water carries it by a small gutter into the fore pit, where it makes its first settlement, the lighter particles running forward with the water into the middle pit, and thence into the third, where what is called the slime, or finest portion, settles; from these pits the ore is carried to the Keeve, which is a large vat containing water, in which it is farther purified by an operation called tozing, and which consists in stirring the water round by means of a small shovel, with such velocity as to keep the tin stuff in a state of suspension, until the whole quantity which can be managed by one operation is thrown into the vat, and when the Tozer slackens his efforts, the Tin subsides to the bottom, from its greater specific gravity, leaving the sand and other impurities at the top; while this is going on the upper part of the vessel is beaten with mallets for some minutes, in order more effectually to ensure this separation.
A third process still remains to be described, that of Dressing the sand on an inclined plain with the assistance of a small stream of water; a great degree of manual dexterity is here requisite; the object, however, is effected with less trouble and expense, and much more completely, by the German "Repercussion Frames," of which there is a model in the Geological Museum at Penzance.
Upon the same mechanical principle of separation, founded on the relative specific gravities of the Tin oxide, and the earthy matters with which it may be mixed, the Tinner is at once enabled to estimate the value of any given sample of ore; for which purpose the Tin stuff is placed on a shovel, and washed under a stream of water, until the impure earthy particles are carried off from its sides, when by a peculiar and dextrous motion, not easily described, all the particles of the ore are collected together on the fore part of the shovel. This operation is called Vanning.
When the Tin ore is contaminated with Mundic, that is, with Arsenical and Iron Pyrites, it is first roasted in the Burning House, and then washed; by which means the Tin, which is heavy, is easily separated from the other ores, which are comparatively light. If any Sulphuret of Copper be present, the same process is calculated to separate it, by thus converting it into a Sulphate,[108] as described at page [128].
When the ore is dressed, the lord of the soil receives that portion which is his due, after which it is divided into as many doles or shares, as there are adventurers; and these are measured out by barrows, an account of which is kept, in the manner of the old times, by a person who notches a stick.
The manner of dressing and cleansing Copper ore is nearly similar to that of Tin, except indeed that as it is raised in large masses, and is tolerably pure, it does not generally require Stamping, nor much washing.