« VorigeDoorgaan »
48. The Daemons of the mine restrains, &c.] In order to prevent, as much as possible, the collieries from being filled with those pernicious damps, it has been found necessary carefully to search for those crevises in the coal, from whence they issue out; and at those places, to confine them within a narrow space; and from those narrow spaces in which they are confined, to conduct them through long pipes into the open air; where being set on fire, they consume in perpetual fiames, as they continually arise out of the earth.
49. And summons, &c.] Those who have the direction of these deep and extensive works, are obliged to use great care and art in keeping them continually ventilated with perpetual currents of fresh air; which afford the miners a constant supply of that vital Auid, and expel out of the mines damps and other noxious exhalations, together with such other burnt and foul air, as is become poisonous and unfit for respi. ration.
ib. Nor strikes the flint, &c.] It having been observed by Mr. Spedding, who superintends these collieries, and to whom the author here gives the name of Prospero, that the fulminating damp could only be kindled by flame, and that it was not liable to be set on fire by red-hot iron, nor by the sparks produced by the collision of Aint and steel; he invented a machine, in which, while a steel wheel is turned round with a very rapid motion, and flints are applied thereto, great plenty of fiery sparks are emitted, that af. ford the miners such a light as enables them to carry on their work in close places, where the flame of a candle, or lamp, would occasion dreadful explosions. Without some invention of this sort, the working of these mines, so greatly annoyed with these inflammable damps, would long ago have been impracti. cable.
50. But on You move, &c.] The reader may suppose that he hath entered these mines by the opening at the bottom of a hill, and hath already passe 1 through a long adit, hewn in the rock, and arched over with brick, which is the principal road into them for men, and for horses; and which, by a steep descent, leads down to the lowest vein of coal. Being arrived at the coal, he may suppose himself still to descend, by ways less steep, till, after a journey of a mile and a half, he arrives at the profoundest parts of the mine. The greatest part of this descent is through spacious galleries, which continually intersect other galleries ; all the coal being cut away except large pillars, which, in deep parts of the mine, are three yards high, and about twelves yards square at the base ; such great strength being there required to support the ponderous roof.
ibid. A triple story, &c.] There are here three strata of coal, which lie at a considerable distance one above another. The mines wrought in these parallel strata have a communication by pits, and are compared by the author to the different stories of a building:
50. Thick Acherontic rivers, &c.] The water that Aows from the coal is collected into one stream, which runs towards the fire-engines. This water is yellow and turbid, froin a mixture of ocher, and so very corrosive, that it quickly consumes iron.
ibid. How, breathless, with faint pace, and slow, &c.] Those who descend into these mintes, find them most close and sultry in the middle parts, that are most remote from the pits and adits, and perceive them to grow cooler the nearer they approach to those pits which are sunk to the deepest parts of the mines; down which pits, large-streams of fresh air are made to descend, and up which, the water is drawn out, by means of fire-engines.
51. Where Earth, &c.] The vein of coal is not always regularly continued in the same inclined plane, but, instead thereof, the miners frequently meet with hard rock, which interrupts their further progress, At such places there seem to have been breaks in the earth, from the surface downwards; one part of the earth seeming to have sunk down, while the part adjoining has remained in its ancient situation. In some of these places, the earth may have sunk ten or twenty fathoms, or more; in other places, less than one fathom. These breaks, the miners call Dykes; and when they come at one of them, their first care is to discover whether the strata in the part adjoining be higher or lower than in the part where they have been working : or, (to use their own terms) whether the coal be cast down, or cast up. If it be cast down,
they sink a pit to it; but if it be cast up to any considerable height, they are often-times obliged, with great labor and expence, as at the place here described, to carry forwards a level or long gallery through the rock, until they again arrive at the stratum of coal,
51. Whose roofs, &c.] These colors, with which the free-stone roof of the mines is beautifully variegated in many places, and which have the appearance of clouds, seem to proceed from exsudations of salts, ocher, and other earthy substances.
ibid. While pent within the iron womb, &c.] The author hath here taken occasion to celebrate the fire. engine, the invention of which does such honor to this nation. He has endeavored to describe, in a poetic manner, the effects of the elastic steam, and the
great power of the atmosphere ; which, by their alternate actions, give force and motion to the beam of this engine, and by it, to the pump-rods, which elevate the water through tubes, and discharge it out of the mine. It appears, from pretty exact calculations, that it would require about 550 men, or a power equal to that of 110 horses, to work the pumps of one of the largest fire-engines now in use, (the diameter of whose cylinder is seventy inches) and thrice that number of ·men to keep an engine of this size constantly at work. And that as much water may be raised by an engine of this size kept constantly at work, as can be drawn up by .2520 men with rollers and buckets, after the manner now daily practised in many nines; or as much as can be borne up on the shoulders of twice that number of men; as is said to be done in some of the mines of Peru.-So great is the power of the air in one of those engines.
There are four fire-engines belonging to this col. liery; which, when all at work, discharge from it about 1228 gallons every minute, at thirteen strokes; 1,768,320 gallons every twenty-four hours. By the four engines here employed, nearly twice the above. mentioned quantity of water might be discharged from mines that are not above sixty or seventy fathoms deep, which depth is rarely exceeded in the Newcastle collieries, or in any of the English collieries, those of Whitehaven excepted.
The reader may find an account of Savery's engine in Harris's Lexicon Technicum.-Many great improvements have been made to it since, and are daily making; several of which are relaied in the Philosophical Transactions. The best account of it, its various improvement and uses, is, I think, in Dr. Desaguliers's course of experimental philosophy, vol. 11.
52. Above your heads, &c.] The mines are here sunk to the depth of one hundred and thirty fathoms, and are extended under the sea to places where there is, above them, sufficient depth of water for ships of Jarge burden. These are the deepest coal-mines that have hitherto been wrought; and perhaps the miners have not, in any
of the globe, penetrated to so great a depth below the surface of the sea; the