the stone is but lightly impregnated with tin, it is said to be just alive; when it contains no metal it is called dead; and the heaps of rubble are emphatically called deads.

TIN SMELTING.

The following description of the process by which Cornish tin is produced is taken from Dodd's 'British Manufactures,' pages 162, 164:

"The ores found in veins and that of the stream-works are subjected to different processes of smelting, for they produce metal very different in point of purity. That obtained from mine tin is always of inferior quality, owing to the mixture of other metals, and which it is probable could not by any mode be got rid of; it is known in commerce by the name of common or block tin, and the quantity produced forms a large proportion of the whole that is brought to market. Stream tin produces a superior metal, known by the name of grain tin, which is principally used by the dyers and for the finer purposes. The first operation after the mine tin is brought to the surface, is to break it into pieces the size of a man's fist, and to reject such portions as do not contain more ore than will repay the cost of dressing, the first great operation in the smelting process.

"As the ore is sometimes so scattered through the stone as to be scarcely perceptible to the eye, the workman from time to time reduces a small quantity to an impalpable powder; and, by repeatedly immersing it in water and shaking it on a shovel, the heavier metallic particles separate from the lighter impurities, and in that way the quality of the ore is ascertained. The ore roughly broken, is taken to the stamping mill, which consists of several heavy upright wooden beams, shod with iron, and raised successively by wheels set in motion either by a steam-engine or water-wheel, and the ore passing beneath these beams in succession as it becomes smaller and smaller, and through sieves of various boxes under the surface of water, is at last brought to the state of coarse powder.

"This powder is now subjected to a great variety of washings and siftings, in all of which the purpose is to take advantage of the high specific gravity of the ore, and so to separate it mechanically from the lighter stony substances with which it is united in the vein. All these operations are conducted with more than ordinary care, for as the ore contains so large a proportion of valuable metal, it is important to guard against waste. But being sometimes mixed with other metallic ores which, from their specific gravity approaching so near that of the tin, cannot be removed by any process of washing, and these being for the most part decomposable by heat, the pounded ore is roasted in furnaces with a moderate and regular fire. After which it is again washed, and the tin ore, which is unalterable by that low heat, is obtained in a greater degree of purity.

"It is now in a state to yield from fifty to seventy-five per cent. of metal, and it is then sold to the smelter, who determines its value by assaying a sample carefully taken from the whole quantity.

"The smelting-furnaces hold from 12 to 16 cwt. of ore, and this is mixed with certain proportions of coal and slacked lime.

"The ore is an oxide of tin; the carbon of the coal unites with the oxygen, and thus the metal is set free, the lime acting as a flux to assist the melting. The heat employed is a very strong one, and such as to bring the whole mass into fusion, and is continued for 7 or 8 hours.

"The liquid tin is run off into an iron kettle from a hole in the bottom of the furnace, leaving the slag or impurities behind.

"The tin is ladled into moulds to form plates of a moderate size to be refined by an after process. The impurities still adhering are generally iron, copper, or arsenic, and these are separated by fresh meltings and exposure to heated air; and then the pure tin is cast into granite moulds capable of containing somewhat more than 3 cwt. each.

"These are called blocks, and are sent, according to the provisions of the Stannary laws, to be stamped (or coined as

it is termed) by the Duchy officers, and it then comes to market under the name of block tin.

"The stream tin ore, after being dressed by poundings and washings, is carried to a blast furnace, where, being mixed with wood charcoal, it is subjected to a very powerful heat urged by bellows moved by an engine. The melted tin is received in an iron kettle under which there is a gentle fire, and it is kept in agitation by plunging pieces of charcoal which have been soaked in water into it, and which by means of an iron tool are kept at the bottom of the kettle, the water in the charcoal is rapidly converted into vapour, and so the agitation is kept up, and any impurities in the tin are thrown up to the surface and skimmed off, and then the metal, which is peculiarly brilliant in appearance, is removed by ladles into moulds to form blocks: this is grain tin."

ADULTERATION OF TIN.

It appears from the following extract, taken from the 'Gallery of Art and Nature,' that in early times dishonest traders were accustomed to adulterate tin with lead, and that the Dutch made a fraudulent use of counterfeit stamps to pass off this adulterated tin for English:

“The natural variety in the purity of tin, though sufficiently discernible, is far less than that which is fraudulently introduced.

"Tin is more than five times as expensive as lead, and as a mixture consisting of a large portion.of tin with a small one of lead cannot easily be distinguished from a mass of pure tin, the temptation to adulterate is great and the fear of detection small. In Cornwall the purity of tin is ascertained before it is exposed to sale by what is called its coinage, the tin, when smelted from the ore, is poured into quadrangular moulds of stone containing about 320 lbs. weight of metal, which when hardened is called a block of tin. Each block of tin is coined in the following manner: The officers appoined.by the Duke of Cornwall assay it by taking off a piece of one of the under corners of the block,

partly by cutting and partly by breaking; and if well purified they stamp the face of the block with the impression of the seal of the Duchy, which stamp is a permission for the owner to sell, and at the same time an assurance that the tin so marked has been purposely examined and found merchantable."

This rude mode of assay is not wholly improper, for, if the tin be mixed with lead, the lead will by its superior weight sink to the bottom, and thus be liable to be discovered when the bottom corner of the block is examined. But though the seal of the Duchy may be some security to the original purchasers of block tin, it can be none at all to those foreigners who purchase our tin from Holland, for if we may believe an author of great note, "in Holland every tin founder has English stamps, and whatever his tin be, the inscription, block tin, makes it pass for English."

"In buying and selling the fault of the Dutch

Is giving too little and asking too much."

SUBMARINE TIN MINES.

It is a most remarkable fact that, in the eager search for tin, some of the Cornish mines have, in defiance of danger, been carried to a considerable distance beneath the sea. The following description is given of the mine Huel-Cok in the parish of St. Just:

"In some places the miners have only three fathoms of rock between them and the sea, so that they hear very distinctly the movement and the noise of the waves.

"The loudness of this noise is sometimes terrible, as the Atlantic Ocean is here many hundred leagues in breadth. In the mine the rolling of the rocks and stones overhead, which the sea moves along its bed, is plainly heard, the noise of which, mixed with the roaring of the waves, sounds like reiterated claps of thunder, and causes both admiration and terror to those who have the curiosity to go down. In one place where the vein was very rich the miners searched it