MINE. 



815 



\V 



under Uip- 



coal a ; and b, c, d, c,f, coals lyirrg above the coal a ; 

 the coals which lie below it g, k, i ; k is die forehead 

 ofth:- mine intersecting all the lower coals ; 



and / the other forehead of the mine intersecting all the 

 u]i)K-r coals. 



An additional breast of coals, as in the above case, 

 <--d, by sinking the engine-pit deeper, ami 

 running level cross-cut mines, as above mentioned. But 

 .this plan is not easily accomplished, if the water is hea- 

 vy in the pit. If it is so, the plan is to connect the 

 wind-bore of the lower set of pumps with a kneed 

 pipe, and make a lodgment for the water in the coal 

 to the dip of the engine-pit bottom; to the dip hand 

 of which tail pipes are laid from the kneed pipe, as re- 

 presented in Plate CCCXC I V. Fig. 6, where the knee 

 of the pipes rests on a strong bunton. By this plan no 

 water descends the shaft while sinking. The addition- 

 al depth is represented by the dotted lines; and the 

 double horizontal dotted lines represent the cross-cut 

 mines for the coals a dipping. 



Another plan of working a coal under dip of the en- 

 gine-pit bottom, is by means of what is termed an in- 

 verted syphon, known also by the name of a drowned 

 or blind level, as represented in Fig. 7, where A is an 

 engine pit sunk to the coal B, and C is a coal 10 fa- 

 thoms deeper, and dipping 1 in 12. The pit is sunk 

 to the coal C, and a mine is run in that coal a dipping 

 to the distance of 120 fathoms to the point D. This 

 distance is found by multiplying the distance betwixt 

 -o coals by tfaedip, viz. 10 x 12=120. While the 

 . ing, a similar mine is driven in the coal 

 B immediately above, and in the direction of the mine 

 > the point E, above the forehead D. From E 

 i blind pit is Mink, or one or more bores are put 

 down, by which all the water found in the coal from B 

 to that when the water rises to the top 

 of the blind pit at E, it discharges into the engi: 

 Minip at C. By this operation, a new breast of coal is 

 . > fathoms in breadth, and the whole 

 length of the coal-field. The same effect would have 

 been obtained, by running a stone mine, or cross cut in 

 the direction of the dotted line CE ; but the first opera- 

 tion being in coal, the expence is almost nothing in com- 

 parison with what the cross cut mine would cost ; and 

 if a greater breast of coal was necessary., under-dip ope- 

 rations wou'd commence at E, and the water thereof 

 be delivered into the blind pit. This second portion of 

 under-dip coal would require to have pump* from E a 

 If, and these could be wrought by any of the 



Another method of gaining under-dip coal, where 

 pits are not deep or very expensive, is to run a mine 

 in the coal to any distance a-dipping, as from C to F; 

 then to begin a pit H upon the surface, so as to bv 

 directly above the forehead F. As soon as the pit is 

 secured to the rock-bead through the alluvial cover, a 

 bore is put down to the mine at F ; by this means all 

 the water found in the pit descends through the bore, 

 and ascends the mine to the bottom of the engine-pit 

 at C ; by this method the pit is sunk to the depth G 

 without being troubled with water. G being on a 

 level with C, the water or growth of the pit must then 

 either be drawn up the pit H or the pit A, until the 

 pit 1 1 is sunk to the coal at F. A set of pipes is then 

 laid along the pavement of the coal from C to F, and 



Mines of 

 Coal. 



growth of the water, is placed from the suinp ai F to 



the height of the trough at G ; and the pump-spears 



are connected with the coal-drawing engine at the 



mouth of the pit. Hence all the growth of water in un( t er ^p- 



the pit is conducted into the trough upon the top of coals, 



the pipes, and into it also the water from the pumps is 



delivered. The water by its own gravity ascends the 



pipes from F to the engine-pit bottom at C, where it 



is drawn to the surface by the main engine. 



The foregoing plans for working under dip coil--, 

 are such as are in general practice. Of these plans 

 there are many modifications and combinations, to suit 

 the particular situation of a colliery. 



In prosecuting the workings of under-dip coals, it 

 requires caution not to carry the rooms or boards 

 through upon the level or dip-head mine of the first 

 winning, as in this case all the water of that winning 

 would descend to the under-dip works and drown 

 them. This caution is particularly necessary when 

 approaching the dip-head levels of a level free coal, 

 for, if not attended to, the water of the level free coal, 

 in place of going out by the day level, would go down 

 upon the engine a dipping and overpower it ; in all 

 such cases strong barriers of coal ought to be left upon 

 the dip-side of the dip-head levels, not only to keep 

 the water up, but to resist any crush or sit in the coal, 

 which would have the effect of letting down the water 

 also. 



In the working of coal mines, serious interruptions Inurrup. 

 occasionally take place, even with every precaution in tion in 

 the management. These interruptions arc, chief- mining. 



1st, Creeps. 



2d, Crushes, thruits, or sits. 

 3d, The coal taking 

 4th, Water in extra qu.mtily. 



A creep is occasioned from the pavement being very Creeps, 

 soft, and the pillars of small area, :o that they sink 

 into the pavement and produce a movement in all the 

 sup-i incumbent strata. If once the creep begins, it is 

 1 impossible to prevent it ovcrruning all the 

 workings. If the soft pavement is iliin, it will only 

 heave up a little, and no great injury will arise to the 

 works; but if the pillars arc very weak, they are lia- 

 ble to give way and produce a crush. When the 

 soft pavement is of considerable thickness, the pillars 

 sink very much, until the upheaved pavement meets 

 the roof, and shuts up the workings altogether. This 

 misfortune is generally rectified by driving mines 

 through the creep to the whole coal wall, and then 

 opening up the works anew. From the improved sys- 

 tem of mining introduced at Newcastle, the pillars in 

 the creep are frequently wrought by taking away the 

 upheaved pavement. This operation lias been greatly 

 facilitated since the introduction of the safety lamps. 

 The only effectual plan for preventing creeps, is to 

 work the mines with narrow boards, and very large 

 pillar*, which is no lois, as all the pillars can be got 

 out afterwards. 



A crush is produced in general by the pillars being Criuhei. 

 left too small to resist the weight of the superincum- 

 bent strata; or it is produced sometimes where the 

 pillars are abundantly strong, but where the strata in 

 the roof are very soft, and composed of argillaceous 



, earth or fire-clay ; this kind of roof breaks along the 



up from the pit-bottom a few feet higher than side of the pillars, and falls down, after which the 



there a trough is placed on the top of them, fire-clay above the heads of the piljars crumbles, from 



if pumps, of a diameter corresponding to the the pressure and exposure to the air, and a crush tn- 



