332 



MINE. 



Mines of 

 foal. 



Searching 

 (or coal. 



Starching 

 for lime- 

 stone. 



Searching 

 for iron- 

 stone. 



Filling or 

 winning a 

 coal-field. 



ss fuel, is near Exeter in Devonshire. As its existence 

 in any district of country cannot be traced by analogy, 

 as coals can be, from a regular series of rocks, no rules 

 can be given as to searching for it ; and it is appre- 

 hended that this kind of ligneous deposit is but spar- 

 ingly scattered over the globe. It is found in Europe, 

 in the districts of Germany, Denmark, Prussia, Italy, 

 Greenland, and the Faroe Islands; and probably exists 

 in other quarters of the globe. The drift-wood which 

 has greatly accumulated, and continues to accumulate, 

 along the sides of some of the great rivers of America, 

 will, it is very probable, at no very distant period, be 

 covered with alluvial soil, and be converted into bovey 

 coal. From this view of its geographical position, it is 

 more likely to be found in the recent than in the old al- 

 luvial cover ; and more probably not very distant from 

 the line of junction betwixt them, where the rising 

 grounds point out to the eye great districts of country, 

 which very evidently were occupied by water previous 

 to the extensive districts of rich alluvial lands being 

 formed by deposits from the rivers. 



In surveying a district for coal, both lime and iron- 

 stones may be discovered. In some instances, lime- 

 stone forms the roof of coal, but in the extensive coal 

 districts, the thick and valuable beds of limestone are 

 found in the lower series of the strata, under all the 

 main beds of coal. Limestone being very hard, and 

 not easily decomposed, frequently crops or bassets out 

 to day, hence more lime rocks have been discovered 

 by surveying the surface than by any expensive pro- 

 cess of boring. 



In searching for ironstone, it is frequently found ex- 

 posed to view in the broken ground ; but if this is not 

 the case, numerous small pits must be sunk along the 

 district under survey, and a series of bores put down if 

 necessary. Few fields of ironstone have been fitted to 

 a great depth, and drained with machinery. The 

 greater part of the ironstone mines in Great Britain 

 are either wrought level free, or are drained and 

 wrought in connection with coal mines in the same 

 stratification. 



Having thus described the position of coal in a geo- 

 logical point of view, particularly its relation to the 

 other strata composing the upper part of the globe ; and 

 having also stated the kinds of alluvial cover which rest 

 upon it, the dislocations incident to the strata, the 

 changes in the beds of coal termed troubles, the mode 

 of surveying a country for coal, the process of boring 

 for it, and ascertaining the different strata, the next 

 department of mining to be described, is, the manner 

 pursued to render a coal workable ; termed the fitting 

 or winning of a coal. 



If a coal, or a number of coals, are found to exist in 

 a coal-field, the first obstacle which prevents a pit's be- 

 ing sunk to any considerable depth is water, which is 

 generally found in great quantity, particularly in the 

 first opening of a coal-field, (if the pit is sunk near the 

 crop,) which water, whether found in pits of very mo- 

 derate or very great depths, proceeds from the surface 

 of the earth, though a contrary opinion was once held ; 

 it being evident and certain, that the source of all wa- 

 ter found in mines is rain, which percolates through 

 the alluvial cover, excepting in those cases when coals 

 are wrought under the waters of the ocean ; for, it was 

 shewn in the vertical section of the strata, that every 

 stratum, however deep it may be from the surface in 

 any one place of a coal-field, always rises till it meets 

 the alluvial cover, comes to day, or crops out, as it is 

 termed, excepting it is met by a slip or dislocation of 



the strata. If the crops of the strata are covered with Mine of 

 alluvial matter containing water, such as gravel, quick Coal 

 sand, or any kind of soil pervious to water, this water Vawy.*^ 

 will percolate through the pores, fissures, and beds of Winning a 

 the strata, and force its way into that place of the pit coal-field, 

 or mine where the lateral resistance is taken away. If 

 the strata crop out into bed. of rivers, this circumstance 

 produces, in general, an uncommon growth of water in 

 the coal and adjoining strata. 



From the circumstance of the water being so abun- 

 dant in coal-fields, and presenting such an obstacle to 

 the operations of the miner, coal-fields are divided 

 into two kinds, viz. 



1. Level free coal. 



2. Coal not level free. 



The level of the surface of the ocen being the low- 

 est point for drainage upon the surface of the globe, 

 all coals and strata situated at a higher level than this 

 surface are physically level free ; and all coals and stra- 

 ta situated under that line are physically not level free. 

 Therefore, in a general point of view, the surface of 

 the ocean is strictly the line which divides these por- 

 tions of coal-fields which are level free, from those 

 which are not level free. 



Though this definition is true in a philosophical point Coali lerel 

 of view, many coal-fields, though level-free, are situated free - 

 at such a distance from the shores of the ocean, or arms 

 of the sea, that the cxpence of bringing up a level or 

 mine would be so great as to render such an operation 

 out of the question ; and therefore, in the practice of 

 mining, if a coal-field, or portion of it, is so situated 

 above the surface of the ocean, that a level can be car- 

 ried either from that point, or from any hollow ground 

 inland, till it intersects the coal, such field of coal, situat- 

 ed above the point of intersection, is termed a level free 

 coal ; whereas if a coal-field, though situated above the 

 level of the ocean, cannot, on account of the expence, be 

 drained by a level or mine, but by machinery, such 

 coal-field, or portion of a coal-field, so drained, is, in 

 the miner's language, termed not level free, though it is 

 physically so. 



From these principles, it is obvious that all coals and Coal not 

 minerals situated under the level of the ocean must of * evel ' 

 necessity be drained by machinery ; and that all coals 

 situated above that level may be either wrought level 

 free, or by machinery, as may be thought most expe- 

 dient. This expediency is a matter of calculation ; viz. 

 whether, in draining a given area of coal-field, the esti- 

 mated expence of driving the level, and upholding the 

 same in repair, is less than the estimated expence of 

 erecting an engine with all its appendages, taking into 

 calculation the annual expence of working and uphold- 

 ing the same ; to which must also be added, a sum for 

 contingencies. It must also be considered, that the le- 

 vel is constantly effectual in its operation, and is not af- 

 fected by additional feeders of water ; whereas each ad- 

 ditional feeder of water to an engine always produces an 

 additional expence ; besides, the engine wears out, and 

 must be renewed, or, if sold at any time, does not in ge- 

 neral bring one- third of the first cost. In these calcula- 

 tions must be considered the time required for complet- 

 ing the winning in both ways ; and if the time requir- 

 ed for executing the level greatly exceeds that for erect, 

 ing the engine, this circumstance alone may, in some 

 cases, produce a determination to erect an engine in 

 preference to making a level, though the latter was found 

 in calculation to be absolutely less. There are instances, 

 however, where, in order to save time, it may be expe- 

 dient to make a partial winning, of little depth, either 



