700 



GEOLOGY. 



Seam dipping. 



outlay of capital incom 

 patible with a profitable 

 return. The labourer 

 has to work in these narrow seams 

 either on his knees, or in a less 

 erect position, his helpers drawing 

 the skiffs of coal cut away upon 

 all-fours. When the seam dips 

 at a considerable angle, the coal is 

 drawn up the incline to a level by 

 means of a windlass, as represented. 

 Every pit which has been worked any length of time contains a number of these 

 excavated seams, one above another, connected by trap stairs, all lying below the 



bottom of the shaft of the mine, to which the coal has to 

 be carried. The height ascended, with the length of the 

 lateral passages, is often a journey equal to the ascent of 

 St. Paul's, but far more laborious, owing to the burdens borne 

 by the coal-bearers. Sometimes the subterranean highways, 

 instead of being connected by a trap staircase, are severally 

 reached by a " turnpike stair," a gradually ascending, spiral, 

 unrailed road. Besides the exhausting nature and the dreary 

 scene of their toils plying with blackened arms the pick 

 axe, a hundred fathoms deep below the surface of the soil, in 

 damp and darkness which a few flickering lamps serve but 

 to render visible peculiar dangers threaten habitually the 

 mining population, from the possibility of the roof of their 

 subterranean workshop falling in upon them, or the explosion 

 of the inflammable gas evolved from the coal, through contact 

 with an unguarded flame. 



In no part of the world are the coal measures, with the 

 other members of the carboniferous system, so extensively 

 developed, within the same area, as in the British islands. 

 Leaving out of sight the great beds in the lowlands of Scot 

 land, and in Ireland, there are in England and Wales the following fields, the arrange 

 ment of which is adopted from Conybeare and Phillips : 



COAL DISTRICT NORTH OP THE TRENT, OR GRAND PENINE CHAIN. 



1. Field of Northumberland and Durham, stretching from the river Coquet on the north 

 to the Tees on the south, a distance of fifty-eight miles, by a breadth, at the greatest, of 

 twenty -four. 



