MINE. 



345 



CoaL 



g 

 coal-field. 



('. - :n 

 pil*. 



Sccurinf 

 the tbafl 

 wall*. 



Mines f ries of Great Britain are wrought by means of an en- 

 gine-pit, and a series of pits, sunk at regular distances, 

 . the system of the colliery. The expense of 

 being comjjaritively very little, they are of 

 various -liapcs, as before mentioned. When circular 

 tb.ry.are about eight feet in diameter ; when 

 ju'ar, they are eleven feet long by five feet 

 broid The long elliptical pits are eleven feet long by 

 (even feet wide. 



Common pits are in general easily sunk after the rock 

 head is found, and the cover secured, particularly 

 when the growth of water is such that no tubbing is 

 required. The process followed is to drive a mine to 

 the place where the pit is intended to be, and having 

 fixed the spot above irround from a survey made, the 

 instant the pit ia gunk to the rock head, a bore is put 

 down to the mine, by which all the water descends, 

 which aids the ventilation of the pit. In all rectangu- 

 lar pita, a small counterfort or bracket of rock is left 

 at each corner, termed a pane, which strengthens the 

 idea of the pit, and render* the sinking or walling of 

 the pits easier. When the alluvial cover i* secured by 

 masonry of ruble work in square pita, it U the practice 

 to throw arches of Ashler stone in a vertical direction 

 at every three or four fathoms distance. These strength- 

 en the aides against the lateral pressure. 



In the coarse of sinking, if any very soft strata are 

 found, which have not consistency to form a firm shaft 

 wall, a recess is cut oat tietwixt the firm strata upon 

 the lower and upper aide of the soft strata, and walls of 

 maaonry substituted, either of brick or of stone ; and if 

 beds of greenstone occur, or any very hard rock which 

 will not wall smooth, but which, in blowing with gun- 

 powder, leave large angular projections, such strata re- 

 quire to be walled down an extra width, in order to 

 admit of masonry to form smooth side*. In all caaes 

 great attention ia necessary to have the shaft walla M 

 smooth as possible, that is, free from all projection* and 

 hollows, in order that when coals re drawn up with 

 velocity, the basket or hutch may |>a* in a line as tru- 

 ly perpendicular as poscible, otherways, if they touch, 

 they are thrown first tn the one tide and then to the 

 other, and continue a destructive oscillation, both in 

 the ascent and descent, and do much ii jury to the 

 coals, baskets, and pit. Where hutches are need made of 

 deal, the injury thus produced is uncommonly great. 

 When the workmen ride the shaft in going and return- 

 ing to their work, the greatest attention must be paid, 

 in order to have the shaft walls not only very smooth, 

 but all the friable strata secured, because in deep shaft* 

 a very small bit of stone falling from a great height 

 upon the head ol a man prove* fatal. In some shafts, 

 when the strata are chiefly of the various kinds of clay 

 and argillaceous schiatus, they are cased from top to 

 bottom with deals neatly jointed and hailed to ci . 

 buntons fixed to the shaft walla ; for the same cause 

 one pits are built with brick or ashler from the bot- 

 tom to the top. 



The various processes pursued in working coal, and 

 bringing it to market, have now to be detailed. 

 Working of Coal, a* one of the various strata of a coal field, 

 eoai. lies in a conforming situation with the other strata, 



like the leaves of a book; the stratum which rest* imme- 

 diately on it ii named the roof, and the stratum noon 

 which the coal rests i* named the pavement, and in 

 some district*, the thill. The terms roof and pavement 

 are very appropriate, a* the one i* the roof or ceiling 

 to the miner immediately above his head, and the 

 other ia that on which be walk*. It U very remark*. 



VOL. X4T. SO. I. 



. , 



ble in the natural history of coal, that the stratum up- Mines of 

 on which coals generally rest, is an argil or fire clay Coal. 

 of various hardness, from the tenth of an inch to many 

 feet in thickness. When coals rest directly on any 

 other pavement, some trouble or dislocation of the stra- 

 ta is generally the cause. 



A stratum, bed, or seam of coal is not in its texture 

 one uniform solid mas-, nor is it always of a homoge- 

 neous quality. Like the other accompanying strata, it 

 is divided nnd intersected by what are named partings, 

 cutters, reeds, or ends. There are two chief 

 partings in a coal, the one at the pnvemt nt, the other 

 at the roof; these partings are the lines of separation 

 betwixt any stratum and the adjoining one ; sometHMI 

 it is only a fine line running horizontally, and scarcely 

 visible, in other cases it is very distinct, and composed 

 of either a dry powdery matter, or of clay, of n bout a 

 twelfth or an eighth of an inch in thickness. Be- 

 sides these chief paitings at the roof and puvrnunt, 

 there are subordinate partings found in the h-d of coal 

 parallel to these, and sometimes very numerous ; 

 these vary in thickness from a line scarcely vuililo, to 

 a parting of even more than hull' an inch. These parU 

 ings in coal are generally composed of a glimmering 

 fibrous substance, named mineral carbon, which is soft, 

 and when touched blackens the hands very much. It 

 U to be remarked, that this suli-t ::..-. tln.u^ii >ul\, is 

 never found in the backs or cutters of the coal. These 

 partings, backs, or cutters, are delineated in Kig. +. Plate I'I.AT 

 I i C\l I. where A, B, C, D; E, I . <'. I) r. present c.ctci. 

 portion of a bed of coal, the parallelogram A lil>< ' the F 'K- * 

 parting at the roof, and EFO the parting nt the pave- 

 ment; a b, be, tie, and </ the Milmrdinate or intermediate 

 partings ; gh,i k, I m, the badu ; o p. /> tj, r ., * /, r. 

 said the cutters ; from this it is evident that a bed 

 of coal, according to the number of these natural divi- 

 sions, is divided and su!>dividcd into various sized -nlid 

 ig *.!*, of a cubic or rhomboidnl shape, according to 

 the rectangular or oblique direction of the <! 

 one another ; the partings arc always parallel to the 

 roof and pavement, excepting where there are trouble* 

 in the strata, and the backs cross the partings at right 

 angles to their planes. But though cutters are Ii i.n.l 

 sometimes running at right angles to the line of the 

 backs, they n.ore frequently ero*s them obliquely ; so 

 that in the one case the figures formed are rectangular 

 solids, in the other case they are solids of a rl.omboidal 

 florin. 



Beside* these common divisions in the co.nl, there 

 are occasionally found accidental divisions in various 

 directions, but generally in a line somewhat in the >l - 

 rection of the backs, and passing like them from roof 

 to pavement ; these are termed leips or glazed backs, 

 on account of their glossy surfaces, which have no te- 

 nacity as to each other, and are the occasion of : 

 fortunes, some of them fatal to the workmen. When 

 the backs, cutter*, and partings nre good, as the 

 minors term them, they greatly aid their Inbo.ir > 

 working thick beds of coal, particularly where the 

 coal is strong and work* large ; they sre of less im- 

 portance in the soft caking coals, such as are found in 

 the north of England. In strong coals, where the di- 

 visions are good, they are termed back and end coal*, 

 and they break out into pieces of quadrangular form, 

 with smooth planes, and produce comparatively little 

 waste coal, culm, or dross, in the open burning coals ; 

 but where the partings, back;, and cutters are bad, 

 the coal is greatly injured in the working, and much 

 calm is produced, which is cf little or no value. When 

 2x 



