.338 



M I N E. 



M C^I f " er lhe tul> k in g is sunk, till the cover is passed through 

 ^_^_ *-_- alu ^ secured. If the mud is uncommonly soft, and 

 Winning a pumps are used to draw the water, they must be hung 

 coal-field, with tackles, and not allowed to sink down so low as 

 the bottom of the tub, as they would not only be liable 

 to choke, lint they would have a tendency to draw the 

 mud from the back of the tubbing. It is therefore the 

 practice to keep the bottom of the tub several feet in 

 advance of where the workmen stand, and to keep 

 about a foot of water upon the top of the mud. In this 

 way the workmen stand upon pieces of board, to pre- 

 vent themselves from sinking; and the mud is lifted with 

 scoops or shovels under the water. If the mud is of 

 great depth, the tubs must be strengthened with addi- 

 tional cribs to resist the pressure. 



Quick. The most difficult operation in sinking, is when the 



cover has a bed or beds of quicksand in it, or has a great 

 bed of quicksand from the surface to the rock head. 

 This circumstance is, in all cases, productive of great 

 additional labour and expence. In the early times of 

 mining, a quicksand cover formed an insurmountable 

 obstacle to the miner; and it is only within the period 

 of a few years past, that the operation could be gone in- 

 to with the hope of ultimate success. As this is one of 

 the most important points in coal mining, and as very 

 large sums have been lost by unsuccessful attempts to 

 sink through the sand, the different proces?es which have 

 been adopted, and most approved of, will be now de- 

 scribed, so that a distinct idea may be formed of them. 



In sinking a pit through any cover, the nature of 

 which is not known, the first thing to be done is to 

 prove it by boring ; when that is done the plan of ope- 

 ration most suitable can then be determined on. 



Beds of quicksand are frequently found covering 

 coal-fields upon the margin of the ocean, or by the 

 sides of rivers. One of the oldest plans for passing 

 through them, is by what is termed casting out ; this 

 is still practised successfully. If the sand lies close to 

 the surface, and does not exceed sixteen feet in depth 

 to the underlying bed of clay or the rock head, the 

 pian ot casting out is adopted ; if it is deeper than this, 

 another process is required. When the depth is about 

 sixteen feet, the first operation is to bring up a surface 

 drain, as low as the situation will admit of, which, in 

 most cases, from the flatness of the surface, is very lit- 

 tle ; then from the point where the centre of the pit is 

 to be, a circular area is marked off, of such a width, 

 that if the pit is to be twelve feet diameter inside 

 when finished, the sand may be excavated in the form 

 of the frustrum of a cone, having the sides sloping 

 at an angle of 45 degrees, which slope is set off at such 

 width as to uncover the impervious clay or rockhead 

 to the width of twenty feet. In this case the mouth of 

 the excavation would be about 52 feet in width. It is 

 of great consequence to carry on this operation very 

 expeditiously ; in some instances from fifty to a hun- 

 dred workmen are employed, and as much of the sand 

 as possible is taken out by horses, carts, and barrows, 

 and lai 1 at a distance. As soon as the water begins 

 to gathei sloping pumps are used, and the water never 

 allowed to accumulate. When the slope renders the 

 using of carts and barrows no longer convenient, then 

 the sand is thrown out by various means, such as by 

 men from one stage to another, by trams and trimi- 

 rods laid along the slope, or by common jack-rolls or 

 windlasses, with ropes and buckets erected upon fram- 

 ing, supported by tresses. Horse-gins are also used, 

 placed at a distance from the pit ; and when the water 

 is very heavy, a small steam-engine is employed ; the 



framing over the excavation being either supported by 

 tresses and stays, or by masts, from which the framing 

 is suspended by tackles. No foundation can be got 

 for the main pumping engine till the pit is built up 

 and the cover made quite secure. If towards the bot- 

 tom of the slope the water is likely to produce a run- 

 ning of the sand, the slope is carefully covered with 

 compact turf, cut from a green sward, which, though 

 a very simple remedy, is frequently quite effectual if 

 applied in time ; for it has been found from experience, 

 that if once the bottom of the slope begins to run, it 

 cannot be stopped in its progress, so that in a short 

 time the whole labour of weeks may be lost. Plate 

 CCCXC. Fig. 12. represents a bed of quicksand I 

 resting upon a bed of impervious clay, which clay c 

 is the immediate cover of the rock. When in this * 

 case the clay is found, the first course of ashler stones, 

 jointed to the radius of the pit, is laid in a true cir- 

 cular position in the centre of the area, and about a 

 foot into the clay ; or in some cases where the clay is 

 not very strong, a circular crib of wood is laid down ; 

 upon this the ashler is built, and as each course of 

 stones is laid, about a foot or fifteen inches of well- 

 wrought clay is regularly beat all around the back of 

 the building, and whatever water comes from the 

 sand, flows up at the back, and is allowed to run over 

 the building into the area of the pit, in order to be 

 pumped up. As the ashler and moating are progres- 

 sively carried up, the space at the back is filled up 

 with sand and rubbish, until the pit is completed at 

 the top, and the surface made suitable for the opera- 

 tions of the colliery. By this plan none of the water 

 found in the sand goes down the pit, but is kept back 

 by the clay moating till it finds a' natural issue at the 

 surface. A is the pit, a a the quicksand, b b the ex- 

 cavation afterwards filled up, c c the ashler building, d d 

 the moating of clay. When this is done, the imper- 

 vious clay is sunk through to the rock head, and se- 

 cured with ashler in the manner mentioned for sinking 

 through compact cover. If the sand rests upon the 

 rock head, and the rock be of a kind which is imper- 

 vious to water, then the ashler is laid upon it as soon 

 as a level foundation is made ; but if it is a porous or 

 jointed stone, it must be sunk through, until a stratum 

 impervious to water is found, from which place the 

 building and moating commence. 



If the quicksand is deeper than sixteen feet, it is 

 thrown out in the first place to that depth, in the 

 manner before described, and the additional thick- 

 ness of sand is passed through by means of strong 

 frames of wood, at the back of which, sheeting-piles 

 are driven down progressively as the sand is taken out ; 

 but this mode of passing through sand is uncertain of 

 success, and is not in general practice. 



The manner of passing through mud with tubbing 

 having been before described, the same kind of opera- 

 tion is applicable to passing through quicksand ; and 

 if the bed of sand is thick, it is passed through by 

 what is termed a drop-tub, that is, after a number of 

 tubs have been sunk by great weights, and begin to 

 get body fast, so that they will not sink any farther, 

 another set of tubs is let down through these, and 

 continued till they reach the rock. These tubs are 

 constructed of such strength, as to resist the pressure 

 and be water-tight. If the tubbing is judged to be 

 too weak at the bottom for the pressure, an additional 

 number of oak cribs are inserted. During the opera- 

 tion, the bottom of the tub which is sinking is kept 

 always a few feet lower than the spot where the men 



Mines of 

 Coal. 



