320 



M I N E. 



Mine? of 

 Coal. 



Troubles. 



Dikes. 



PLJTR 



CCCL1XXVIM. 

 Kte. 1. 



Slips. 

 Fig. 8. 



ig.9. 



1 . Stone in irregular beds. 



2. Nips. 



S. Shaken coal. 



4. Foul coal. 



5. Pyritaceous, or brassy coal. 



6. Sparry coal. 



7. Stoney coal. 



8. Black coal. 



9. Sooty coal. 



10. Dike coal; named, 



a, Burnt coal. 



b, Dander coal. 



c, Humphed coal. 



11. Glazed backs. 



12. Troubles in the roof and pavement. 



The position and effect of these dislocations and 

 troubles have now to be described. 



Dikes, as to their longitudinal direction, are found 

 not only stretching in the line of bearing through the 

 coal-field, but in every direction, sometimes for many 

 miles nearly in the same straight line, while other 

 dikes have irregular deflections, but without sharp an- 

 gular turns. It seldom occurs that great dikes are 

 numerous in a coal district, but the contrary is fre- 

 quently the case with dikes of a small size ; they can 

 only be seen in the beds of rivers, or on the sea-shore, 

 but those of greenstone and basalt, from their superior 

 hardness, frequently rise above all the other strata, like 

 a crest or projecting ridge. 



Dikes of greenstone, of a few feet to three or four 

 fathoms in thickness, are found sometimes very nume- 

 rous, even in a very limited extent of coal-field, not 

 exceeding the area of 200 acres, lying in various 

 directions, and crossing one another. Fig. 7- Plate 

 CCCLXXXVIH. represents the horizontal section of a 

 coal-field, intersected with greenstone dikes. AB and 

 CD are two dikes lying parallel to each other, EF and 

 GH are cross or oblique dikes, which not only divide 

 the coal strata, but divide and separate the dikes AB 

 and CD. In looking at a horizontal section of a coal- 

 field, the dikes, which intersect it, appear to affect the 

 strata no more than the dividing and separating of 

 them, excepting when greenstone dikes occur, in which 

 case, a change of the coal adjoining them is very evi- 

 dent, as will be noticed afterwards, when the effects of 

 dikes upon the strata in the vertical section are treated 

 of. But before entering on this subject, the longitu- 

 dinal direction of slips will be considered. 



Slips run in a longitudinal direction through the 

 strata of a coal-field, and in every obliquity to one ano- 

 ther. Fig. 8. Plate CCCLXXXVIH. represents a ho- 

 rizontal section of a coal-lield, with two slips, AB and 

 CD, in the line of bearing, which throw the strata 

 down to the crop ; this is the simplest form of slips. 

 Fig. y. represents part of a coal-field intersected with 

 slips somewhat similar to a broken sheet of ice. In 

 this Figure, AB is a dike ; all the other lines and ra- 

 mifications in the figure, are slips of every variety and 

 kind, producing dislocations from the least measurable 

 distance to many fathoms; the slips at the points 

 marked a, a, a, disappear ; the lines at C represent 

 four slips of a small size, known by the name of 

 hitches. 



There does not appear any general law as to the line 

 of direction of these slips, only the ramifications are 

 generally more in a dip and rise direction, than in the 

 Ene of bearing of the coal-fields. 



The effects of dikes and of slips upon the coal strata, 

 when viewed in a vertical section, are more evident 



than in the horizontal section, where they only appear Mines of 

 like walls, veins, and lines of simple separation. Fig. Coal. 

 10. is a vertical section of a coal-field from dip to rise, 

 with three strata or beds of coal, a, b, c. AB is a dike P " TK 

 at right angles to the plane > of the coal strata. This 'pi 01 "*! 

 rectangular dike has only the effect of dividing and se- Effects p ro 

 parating the coals, and all the accompanying strata, ducx-d t>y 

 Outproduces no alteration in the line of rise; but fur- dikes, 

 ther to the rise, the oblique dike CD interrupts the 

 coals a, b, c, and not only divides and separates them, 

 but throws them and all their accompanying strata 

 greatly lower down ; but though thrown down, as re- 

 presented in the figure, the coals and strata still keep 

 the same parallelism and direction of rise. Still fur- 

 ther to the rise, the oblique dike EF interrupts the 

 coals a, b, c, and not only divides and separates them, 

 but throws them, and all their accompanying strata, 

 greatly up, and produces a much quicker dip and rise, 

 as represented in the figure. Sometimes the coals in 

 the division H, betwixt the dikes C and E, are found 

 nearly horizontal, and the effect of the dike EF is 

 sometimes such as to throw out the coals altogether, so 

 that no vestige of them can be found in the division K. 

 Such are the most prominent changes in the strata, as 

 to their line of direction produced by dikes ; but of 

 these changes there are various modifications. 



The effect of slips on the strata is represented in the Effects pro 

 vertical section, Fig. 11, where a, b, c, are coals with iluced by 

 their accompanying strata. A B is a slip which intersects ^'P 5 - 

 the strata, and throws all the coals of the first compart- Flg- J1> 

 ment very much lower, as represented in the compart- 

 ment No. 2. ; and, from the magnitude of the slip in 

 this instance, it throws in other coals, marked 1, 2, 3, 

 which were not found in the compartment No. 1. CD 

 represents a slip having the same effect, but not to the 

 same extent. E F represents a slip intersecting the 

 strata, but contrary to the former in its position ; the 

 effect of this is, that the coals a, b, c, are thrown up, as 

 represented in the compartment No. 4. Sometimes this 

 slip brings into view coals situated under these marked 

 a, b, c, such as the coals 4-, 5, 6 ; and when it happens, 

 as we have frequently seen, that a coal marked 4 is di- 

 rectly opposite a well known coal, as e in the copart- 

 ment No. 3, the case is difficult and bewildering to the 

 miner. Besides these varieties, we find a number of 

 slips or hitches often very near to one another, as in the 

 copartment N 7 o. 5, where the dislocation of each slip is 

 not great, but the amount of the whole forms a consi- 

 derable slip as to the coals in the compartment No. 6. 

 These are the general effects of dikes and slips in a 

 vertical section of the strata from the dip to the 

 rise ; whether these dislocations lie in the line of 

 bearing, or with a moderate angle of obliquity to it, 

 that is under 45 degrees. The effects of dikes and slips 

 in pursuing a dead level course direction, are exempli- 

 fied in Fig. 12. Plate CCCLXXXVI1I. Where the coals Fig . u> 

 and accompanying strata are of course horizontal, and 

 the dikes and slips, lying at a greater angle than 4-/J to 

 the line of bearing, they are termed dip and rise dikes, 

 or slips, as AB, CD, EF. 



From what has been stated regarding the effects of General Ian 

 dikes and slips, as to the dislocation of the strata, inde- "g^ding 

 pendently of any changes produced in the coal and ^'. " * 

 strata adjoining, to be noticed afterwards, those who ' 

 are employed in conducting the operations ot collieries, 

 consider that these dislocations follow a general law, 

 which is this: Let Fig. 1, Plate CCCLXXXIX. repre- PI-ATE 

 sent a stratum, or bed of coal, with the accompanying "ctix 

 strata ; A, the pavement of the coal, and B the roof-; if, 



