THE CARBONIFEROUS SYSTEM. 



699 



seriously these derangements interrupt for a time the work of the miner, they are not 

 without their use, acting sometimes as valves by which the water of a mine is drained off, 

 or when filled up with compact matter, they serve as floodgates arresting its course, and 

 preventing its access to deposits which it might otherwise inundate. 



The coal-beds exhibit immense disturbances from the eruption of igneous rocks, the 

 members of the trap family greenstones, clinkstones, and basalts which are associated 

 with them in disrupting, overlying, and interstratifying masses, charring the coal in their 

 neighbourhood, and variously converting it into coke, anthracite, and plumbago. The 

 South Staffordshire coal-field is invaded by a picturesque range of basaltic hills between 

 Dudley and Rowley Regis, and by other eruptions of trap which fill up dykes and faults 

 occurring in the strata. The manner in which the beds of coal have here been disturbed 

 and broken through by protruding plutonic masses, is illustrated in the two sections from 



Imaginary Section before disturbance, 

 a, Lower new sandstone ; b, thick coal seams ; c, thin seams spreading out beneath the seams ; rf, silurian rocks on whirh they rest. 



Mr. Murchison ; the one an imaginary sketch of its appearance while a depositary un- 

 disturbed by the subterranean forces ; the other exhibiting its present shattered aspect 

 as the result of their action. Analogous disruption and dislocations of the coal by trap 

 rocks appear in almost every field. 



Section after disturbance, 

 o, Lower new red sandstone ; b, b, coal measures ; c, thin coal and ironstone ; </, silurian rocks ; e, trap rock 



The working of the coal measures is one of the most severe and dangerous departments 

 of human labour, even when under the most enlightened and humane superintendence, 

 and with capital sufficient to command the application of steam-power as extensively as it 

 can be employed ; but when under the management of a needy or grasping owner, a 

 colliery is equally degrading to humanity and perilous to life. In coal mines of this latter 

 description females were employed at the windlass and at labours still more revolting a 

 spectacle which legislation has recently made an effort to abolish. The master difficulty, 

 however, of many coal-mines, which no law can touch, and which defies the power of 

 capital and the contrivances of humanity, arises from the thinness of the coal-seams, which 

 become the subterranean roadways after the mineral has been extracted, and the distances 

 to which these lateral passages extend from the main shaft, together with the depth 

 below its bottom to which excavation leads. They cannot be traversed except in an 

 unnatural and constrained posture, nor could their capacity be enlarged, without an 



