upper end with the iron sledge or mallet, fig. 7. The hole is occasionally cleaned out by the scraper, fig. 11, which is an iron rod turned up at one end; or if the ground is very wet, and the hole fills with mud, a stick beat at the extremity till it forms a kind of brush is used, and is called a swab-stick.

Holes for blasting are generally about one inch and a quarter in the bore, and of various depths from ten or twelve inches to three feet; but these, as well as the position and direction in which they are bored, and the charge of powder employed, are subject to the skill and discretion of the miner. The rules by which he is guided are to direct the effort of the explosion to a part of the rock which is most easily displaced, and to proportion the charge to the effect required, so as to shake and loosen a larger portion rather than to blow out a less quantity.

Fig. 6 serves to explain the process of blasting, and represents a section of a hole ready for firing. When the hole is bored it must be made as dry as possible; to do which it is partly filled with good tenacious clay and a round iron bar, nearly fitting the bore of the hole, but somewhat tapering, and called the claying-bar; this is driven in with great violence, which so forces the clay into all the crevices of the rock, that, when the bar is withdrawn, the hole usually remains dry. Where this plan fails, from the great flow of water all round, it becomes necessary to use tin cartridges furnished with a stem or tube through which the powder may be inflamed. A section of one of these cartridges is shown in the plate, fig. 13.

When the hole is dry, either by clay, or otherwise, the proper charge of gunpowder is introduced, and the nail, a small taper rod which ought to be made of copper, is inserted, and reaches to the bottom of the hole; the hole is then ready to receive the tamping, which is the most difficult and dangerous part of the process. It is by this that the gunpowder is confined, and the effect produced; different substances are in use for ramming into the hole for this purpose; that most usually employed is any soft kind of rock, which is free from quartz or flinty matter. Small quantities at a time are introduced into the hole, and rammed very hard by the tamping bar, which is held by one man, and struck with a sledge by another; this is continued until the hole is filled up, and the nail being then drawn out by putting a bar through the eye, and striking it upward, leaves a small perforation or vent for the rush which conveys the fire.

The danger of beating the tamping with iron tools in hard rock, and the many dreadful accidents that frequently happen in this operation, have led to the introduction of contrivances to diminish the risk; but, though some of these have been well adapted for the purpose, yet, as they occasion a little more trouble, they have not been generally adopted by the miner. The simplest and best precaution against danger is to have the nail of copper instead of iron; but, as the former is not so easily made or repaired by the smiths on a mine as the latter, they are not so well liked by the workmen.

The other mode of preventing danger in tamping is by employing substances to confine the gunpowder which require little or no force in beating them into the hole, and as dry sand will often serve the purpose if the rock is not very hard it may be sometimes used; but there are many cases in mines where it will not succeed, and therefore it is seldom attempted. A better substance to confine gunpowder in holes is good. tough clay, and this will answer in many cases where sand will fail particularly in wet ground, or in holes that are inclined upwards, it will produce the proper effect in all but very hard rocks, and, if the men could be induced to use it, would undoubtedly tend to the saving many lives.

When the tamping is completely rammed in, and the nail drawn out, a small vent or touchhole remains, which is to receive the rush to communicate the fire. Any small tube filled with gunpowder will answer for this purpose, but nothing is better or more easily prepared than those in common use. For this purpose, the green rushes which grow in wet marsh lands are chosen, and are selected as long and large as can be had. By making a slit in one side, and drawing along in it the sharp end of a piece of stick, the pith may be taken out very completely, and from the elasticity of the skin of the rush the slit closes again. To fill this tube with gunpowder, the rush is held in one hand so as to pass through a small quantity of powder retained in the palm of the hand; and by opening the slit with a small wedge, and pushing the rush along through the powder at the same time, it is made to embrace a quantity sufficient to communicate inflammation.

To fire the hole, one of these charged rushes is dropped through the vent, and is made steady by a piece of clay; a paper snuff is then fixed to the top, which is so adjusted as to burn a sufficient time to permit the man who fires it to retreat to a proper distance.

Fig. 6 represents a section of a charged hole in a rock. The portion which would be dislodged by the explosion is that part included between A and B. The charge of powder is shown by the white part, which reaches as high in the hole as C: from that point to the surface of the rock the hole is filled with tamping, excepting the small orifice which contains the rush, and which has the snuff affixed at D.

Fig. 14 is a drawing of a wheelbarrow, such as is used under ground for conveying ore and waste to the shafts: these barrows are very simple in their construction, and adapted to the narrow and low levels through which they have to pass. They are usually made all of deal, this timber being the most fitted to the purpose. The wheel has a narrow band of iron round it.

Fig. 5 is an iron bucket, or, as it is called in Cornwall, a kibble, and is used for holding the ore and waste while it is drawn up the shafts by machines, worked by horses, called whims. Kibbles are generally made of wood, having very stout staves, very strongly bound with heavy iron binds or hoops; but as those made with iron plates are to be preferred, and need not much. exceed the others in weight, we are glad to be

able to exhibit a drawing of one of the latter of an approved form and construction.

A kibble, such as is used with horse-whims, holds about 300 weight of ore, and 120 kibbles will just clear a cubic fathom of rock.

Miners' work under ground is chiefly divided into sinking, driving, and stoaping.

Sinking is applied to shafts, and to other smaller perpendicular openings from one level to another, usually called winzes.

Shafts are of different, dimensions according to the purposes they are designed for; the largest kind is the engine-shaft, in which are generally placed the pumps for draining the mine of water, the ladders for the men, and a part divided off and called the whim-shaft, for the kibbles to pass up and down. Plate II., MINING, will be found to represent a perspective view of a part of the interior of these shafts.

A good engine shaft measures about eight feet by twelve, though some are sunk of larger dimensions. Shafts intended only for hauling ores through, and those for air and foot-ways, may be about six feet by four.

In large shafts, a set of twelve men are usually employed; in smaller ones eight, or even six, are a sufficient complement to keep the work going. They work two or three at a time, and relieve each other every six or eight hours, keeping good the whole twenty-four without intermission. The miners are attended by laborers, or winze men, who haul up the stuff out of their way

as it is broken.

Sinking is contracted for by the fathom in depth, and the price therefore varies according to the dimensions of the shaft, as well as according to the hardness of the ground, and the circumstances relating to water, air, &c. A medium price is about £20 a fathom for shafts at some depth from the surface, but some have cost £80,

and others are executed as low as £5.

Driving is the term applied to the execution of horizontal passages, which are called adits when used for the conveyance of water near the surface, and levels when made for opening the lode or vein, and forming communications from one shaft to another under ground. Levels ought to be seven feet in height, and two feet and a half wide; by constructing them as high as this, room is given to admit contrivances for ventilation, so that they may be continued to considerable lengths without inconvenience. More than two miners cannot work at one time on the end of a level, and the set of men therefore employed may consist of six, relieving every eight hours, or of four relieving twice in the twenty-four hours, or two men only, who may work as long as circumstances will permit. Driving is paid for by the fathom in length, the height and width being limited; a great variation of prices takes place according as the rock is hard or soft, as work of this sort is done from 10s. a fathom to £30, but about £5 a fathom is the most usual sum paid for this kind of work. These prices here, as well as in sinking shafts, include every expense, as the men pay for their tools, candles, and gunpowder, and likewise are charged with the wheeling the stuff, and hauling

Stoaping is that kind of work which is not included in sinking or driving, but more generally means the breaking away the ground between the levels on the course of the lode or vein, to get the ore. When the men work over head, it is called stoaping the backs, and when the work is carried downwards it is denominated stoaping the bottoms. As both these operations usually take place where ore is obtained, the mode of payment is quite different from that in sinking or driving, and is here called tribute-work, while the other is called tutwork. Tribute means payment by a proportion of the produce, so that the men agree to undertake a particular piece of ground for a certain part of the value of the ore they may procure, when completely merchantable and fit for sale, every operation and process to make it so being conducted at their expense. This mode of contracting is of great advantage to the owners of the mine, as the men have a constant interest concurring with that of their employers, in discovering and procuring the greatest possible quantities of ore, and of returning it in the best and cheapest manner. The proportion paid to the miner, varies of course exceedingly, as many things must be taken into account in estimating a fair tribute for any particular part of a mine, but the contracts are made at so much out of every pound's worth sold, and this fluctuates often in different parts of the same mine from three-pence to fourteen shillings. Nothing shows the necessity of a mine being in the hands of skilful and honorable managers more than the great variation in the prices of all kinds of work carried on in these extensive undertakings.

An engine-shaft is delineated in MINING, plate II.

A, A, A, A, timber-framing put in to support the ground, where, from the rock not being sufficiently hard to stand securely, this precaution becomes necessary. Where boarding is required the planks are driven perpendicularly between the transverse timber and the ground.

B, B, B, B, are dividing-pieces, or beams thrown across the shaft. They serve to support the sides of the shaft, to attach the casingboards to, which part off the whim-shaft from the foot-way and pump, or engine-shaft (it being usual to consider a large shaft of this kind as divided into the three kinds, each bearing its particular name). And, lastly, the dividing-pieces support the ends of the bearers which carry the pumps, ladders, &c.

C, C, C, C, casing-boards which part off the whim-shaft from the other parts; they are stout planks securely spiked to the dividing-pieces, and, when the shaft is not perpendicular, the kibbles slide upon them.

D, the whim-kibble which conveys up the ore and waste, two of which are employed in a shaft, one going up while the other goes down.

E, F, ladders for the workmen, forming what is usually called the foot-way.

G, saller, a small platform at the foot of each ladder.

H, a column of pumps drawing out of a cistern K, which is supplied by a lower tier of pumps I, furnished at the top with a collar

launder J, which delivers into the cistern, which likewise receives the stream flowing from the level at L.

M, a set off, which connects the pump rods, so that one set goes into the column I, and another is continued lower to a deeper lift of pumps.

N, N, N, N, bearers, or timber beams, which support the pumps and keep them steady in their places.

The ventilation of mines is so important a subject that we insert at length the following account of a machine invented and applied to that purpose by Mr. Taylor, late the manager of the principal copper mines in Devon; and for which he received the silver medal from the society for the Encouragement of Arts, Manufactures, and Commerce.

'Next in importance to the means employed for draining underground works from water, may be reckoned those which are intended to afford a supply of pure air, sufficient to enable the workmen to continue their operations with ease and safety to themselves, and to keep up, undiminished, the artificial light upon which they depend. It is well known, indeed, to all who are practically engaged in concerns of this kind, that men are frequently obliged to persevere in their labor, where a candle will scarcely burn, and where not only their own health materially suffers in the end, but their employers are put to considerable additional expense by the unavoidable hindrance and the waste of candles and other materials.

The following remarks are confined to such mines as are worked upon metalliferous veins, according to the practice of this district, and that of the great seat of mining in the neighbouring county of Cornwall, from which indeed ours is borrowed. We find then that a single shaft, not communicating by levels to another, can hardly be sunk to any considerable depth, nor can a level (or, as the foreign miners call it, a gallery) be driven horizontally to any great distance, without some contrivance for procuring currents of air to make up the deficiency of oxygen, which is so rapidly consumed by respiration and combustion in situations like these, where otherwise the whole remains in nearly a stagnant condition.

'We are here unacquainted with the rapid production of those gases which occasionally in the collieries are the cause of such dreadful effects; such as hydrogen gas, or the fire-damp, carbonic acid, or the choke-damp; the inconvenience we experience takes place gradually as we recede from the openings to the atmosphere, and seems to arise solely from the causes which have been before assigned, though it is found to come on more rapidly in certain situations than in others.

'The most obvious remedy, and that which is most frequently resorted to, is the opening a communication either to some other part of the mine, or to the surface itself; and as soon as this is done, the ventilation is found to be complete, by the currents which immediately take place, often with considerable force, from the different degrees of temperature in the subterVOL. XIV.

ranean and upper atmospheres; and these currents may be observed to change their directions as the temperatures alternate.

'The great objection to this mode of curing the evil is the enormous expense with which it is most commonly attended. In driving a long level, or tunnel, for instance, it may happen to be at a great depth under the surface, and the intervening rock of great hardness; in such a case every shaft which must be sunk upon it for air alone, where not required (as often they might not) to draw up the waste, would cost several hundred pounds; or in sinking a shaft it may be necessary, at an expense not much less, to drive a level to it from some other for this purpose alone.

'To avoid this, recourse has been had to dividing the shaft or level into two distinct parts, communicating near the part intended to be ventilated, so that a current may be produced in opposite directions on each side the partition; and this, where room is to be spared for it, is often effectual to a certain extent. It is found, however, to have its limits at no very great distance, and the current at best is but a feeble one, from the nearly equal states of heat in the air on each side. The only scheme besides these has hitherto been to force down a volume of purer air, through. a system of pipes placed for the purpose, and a variety of contrivances have been devised for effecting this; most of them are so old that they may be found described in Agricola's work, De Re Metallica. The most common are by bellows worked by hand; by boxes or cylinders of various forms placed on the surface with a large opening against the wind, and a smaller one communicating with the air-pipes by a суlinder and piston working in it, which when driven by a sufficient force has great power. But the cheapest and most effectual scheme for this purpose, where circumstances will admit of its being applied, is one which was adopted some time since in the tunnel of the Tavistock canal. It is by applying the fall of a stream of water for this purpose, and it has been long known that a blast of considerable strength may may be obtained in this manner, which has the advantage of being constant and self-acting. The stream, being turned down a perpendicular column of pipes, dashes in at a vessel so contrived as to let off the water one way, with an opening at another part for the air, which, being pressed into it by the falling water, may be conveyed in any direction, and will pass through air-pipes with a strong current, which will be found efficacious in ventilating mines in many instances, as it has likewise, in some cases, been sufficient for urging the intensity of fires for the purposes of the forge. It is easily procured where a sufficient fall is to be had; and the perpendicular column can be so fixed as that the water from the bottom may pass off, while the air is forced into a pipe branching from the airvessel, and which is to be continued to the part of the mine where the supply of fresh air is required.

'It has been found, however, that the forcing into vitiated air a mixture of that which is purer, even when the best means are used, though

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