MINE. 



347 



Iliaes of die pavement is found of some considerable extent in 

 v Coal. the line of the dip-head level, the level will then, in 

 ^T^C""", keeping a true level line, assume the form ofahorse- 

 Workmgof ghoe mnd> aft^ p^ing ^ gwe)li win proce ed in its re- 

 gular course as before. 



Having thus stated the general principles upon which 

 dip-head levels are carried in the regular system of 

 coal mining, it will be proper to exemplify the effects 

 of moderate swells and hollows of tin- pavement, a-; the 

 levels proceed onward from the engine pit bottom, as 

 PUTS in Hi- 5 When a hollow occurs, the level is thrown 

 ccxei. to the rise, and, as the hollow decreases, the level 

 Fif. i. s'veeps again to the dip ; whereas, when a swell occurs, 

 the lav-el is thrown a dipping, and, a- the swell dimi- 

 nUhu-s, the level gradually again turns to the rise. In 

 these cases, a sudden turn, or a sharp angle, is never 

 made in t"e mine walls, but the course is pursued by 

 inflections as moderate as the case will admit of. Fnmi 

 what has been stated it is evident that if the miner 

 holds to the dip haw! more than the true level eour-o 

 will allow, he will make what is termed drowned le- 

 vl ; and if he keeps too much to the rise, he will pro- 

 duce what is termed l>*t If- el ; and, if .the lost level is 

 not recovered, the breadth of the breast of coal- tied 

 won will be made narrower, which is a loss, as the 

 ex pence of recovering loet level is often very great. 

 Fig. 8. Fig 8 represent^ a portion of a d-p-head level, w here 

 these errors have been committ d, AU is the dip-head 

 level in its true course, carrying dead water at the fore- 

 head B, from the engine-pit A. a is the fore-head of a 

 piece of drowned level, which must be abandoned, and 

 .left to fill with water, the proper level is regained by 

 Brsaming the work at b, where the error commenced, 

 e is the fore-head of a piece of lost level commencing at 

 d. By this error, the triangle of coal B</, d c, c H, is 

 lost in the winning ; and to correct thi error, the true 

 level must be begun at the point d, and carried dead le- 

 vel to the fore-head B. Drowned levels can never be 

 of great extent, as the water very soon incommodes the 

 workman, and forces him to return. But lout levels 

 sometimes go forward progressively for years, when at 

 last the breast of coal-field becoming evidently much 

 narrower, the true level must often of necessity be re- 

 gained, which requires years of Lbour, and very great 

 expence, all of w h ch might have been saved by correct 

 mining. This therefore shews, that the driving of dip. 

 head levels correctly, particularly in deep winnings, is 

 a point of the very fir.-t im|Kirtance. They ought to be 

 kept clear of ail utones, rubbish, and sediment, as these 

 tend to cause loss of level, by damming the water, and 

 throwing a greater depth "fit at the fore-head than 

 would be if the level was clezr and patent. Wherever 

 the roof is bad, it ought to IK- firmly secured either by 

 carpentry, or by masonry, which is better These be- 

 ing the modes of driving dip-head levels in the diffe- 

 rent kind* of f.iir lying coal-fields, the plans to be pur- 

 sued when dikes, slips, and dislocations occur, have next 

 Pif. 9. to be pointed out Fig. 9 represents a coal-field won 

 by the engine- pit A. a a is the crop, and the double 

 lines proceeding east and west from the engine- pit are 

 the dip-head levels. B and C are two dikes traversing 

 the coal-field in a crop ai;d dip direction, but which do 

 not throw the coal either up or down. \\ hen, therefore, 

 the dip-head level is obstructed bv the dike B, and 

 found to be of that kind which neither throws the stra- 

 ta up or down, then the level is carried thnmi h, as re- 

 presented in the Figure, when the coal wi.i l,e lound 

 on the other side at d. Upon the level proceeding to 

 another dike is found, throwing down the coal ; but 



6 



as the extent of this downthrow is not known, a mine 

 is carried level course, not only through the dike, but 

 several fathoms farther forward, as tof, where a bore is 

 put down, and the downcast proved to be ten fathoms. 

 Thi- being the case, and if the coal clips 1 in 8, then 8x>0 

 is 80, which shews that if a level mine is run in the 

 strata in a direction parallel to the dike, or nearly so a 

 cropping as g H, the coal will be found at h, and the 

 distance will be 80 fathoms as above calculated, provid- 

 ed the roal keeps the same dip and rise as formerly. 

 The dip-head level then proceeds from k eastward in 

 manner as before directed. It must, however, be ob- 

 served. that though the t>tone m:i:c and effect of the 

 downcast have thrown the dip-head level SO fathoms * 

 cropping, the breast of coal from the dip-head to the 

 crop is not narrowed, as the coal upon the east side of 

 the dike will be found to go southward, at least as much 

 farther than the crop upon the west side of the dike, 

 as represented in the Figure. 



In proceeding with the dip-head level westward from 

 the engine-pit A, the slip k u found throwing down the 

 coal and other strata. A mine is carried forward to /, 

 and a bore put down where the slip is ascertained to 

 have thrown down the coal 5 fathoms, hence 5x8 

 gives 40. Therefore if a mine is carried dead level a 

 cropping from m. the coal will be found at n, the dis- 

 tince from m to * bring 40 fathoms, providing the dip 

 of the strata continues the same ; and, in this case, the 

 crop of the coal extends 40 fathoms farther a cropping, 

 as represented in the Figure. The coal having been 

 found at n, the dip-head level proceeds from n to a, 

 where an upthrow slip is found, but the extent of 

 the upthrow unknown. Sometimes the coal is search- 

 ed for, by mining upwards for a few yards ; but the 

 common practice is to run forward a mine a few yard*, 

 and bore upwards, as at p, where the coal is found to 

 be 10 fathoms up ; then 10x8 gives 60. If, therefore, 

 a stone mine is c Tried deud level through the strata a 

 dipping, the coal will be found at r, at the distance of 

 80 fathoms from q, -opposing the dip to be the same as 

 formerly. Rut although the dip-head level is carried a 

 dipping 80 fathoms, no additional bn adth is gained to 

 the breast of coal, as the crop is thrown an equal 

 extent back, as in the Figure. From r the dip-head 

 level proceeds to i, where a downthrow slip is found to 

 be 4 fathom* ; 4 X 8 gives 32. A mine is therefore et 

 off a cropping torn t, but in place of running 32 fa- 

 thoms ere the can! is intersected, it i- found at tin- dist- 

 ance of 2O fathoms at M, which shews that the coal is 

 dipping 1 in 5, in place of 1 in 8. as formerly. This 

 slip runs out, or comes to nothing, as it is termed, in 

 the crop, consequently narrows the breast of coal 20 

 fathoms. Had the dip been rendered less, suppose 1 

 in 20, then it would have required a mine of 80 fa- 

 thom* in place of 20 fathoms to intersect the coal, and 

 it is probable that the breant of coal would have been 

 broader, but this ilt|)<i;cls upon the situation of the- 

 slip towards the crop. When the dip-bead level, as at v, 

 meets with a slip throwing down the coal; and if upon 

 cutting forward, the coal is troubled, the mine mut be 

 continued still forward, till the strata are lound lying 

 regular. In the example given, there are 3 slips or 

 dislocations very near one another, throwing th str.ils 

 atone time up, and at another down, but only a tew 

 feet in exti -in. If upon reaching the point tv, the coal 

 is not found by a bore cither up or down, and if 

 no clear view can ! formed of ine coal-field in that 

 direction, it may beneeevari to txploie the In 1<I by a 

 series of bores put down from the surface. In tlie t'i- 



Mints ot 

 Coal. 



