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_.