282 THE BRITISH ISLES. 



towns which surround the district, and they are gradually extending into the 

 interior of the country. 



The coal measures whiih extend along the coast to the south of the Solway Firth 

 are of considerable importance. At some former epoch the carboniferous forma- 

 tion covered ihe whole of tlie Pennine range, and extended from the shores of the 

 German Ocean to the Irish Sea ; but, owing to the displacement of strata and the 

 actioix of denudation, there are now two separate basins, viz. that of Cumberland, 

 and that of Durham and Northumberland. The Cumbrian coal mines are somewhat 

 famous on account of their submarine galleries. At Whitehaven the levels driven 

 by the miners extend for a distance of nearly 2 miles off the shore, and lie at a 

 depth of 650 feet beneath the level of the sea ; and the entire network of submarine 

 galleries and levels has a length of several hundred miles. The roof which 

 intervenes between the miners and the floor of the ocean varies in thickness 

 between 230 and 720 feet, and is amply sufficient to preclude every idea of 

 danger. Still ihe water of the ocean occasionally finds its way through fissures 

 into the mines, but in most instances the miners succeed in calking the leaky 

 places. The mine of ^Yorkington, however, which extended for 5,000 feet beneath 

 the sea, had a roof too feeble to resist the pressure of the superincumbent waters. 

 On the 30th of June, 18-37, it suddenly gave way, the mine was inundated, and the 

 miners barely escapsd the flood which pursued them. One of these galleries 

 actually extands for a distance of 9,604 feet beneath the sea. The quantit}^ of 

 workable co:il still contained in these submarine seams is estimated to amount to 

 100,000,000 tons.* 



The coal-field of Durham and Northumberland, which is traversed at intervals 

 by parallel dykes of basalt, is more actively worked than any other in Europe. 

 It vields double the quantity of coal produced by all France, and is the principal 

 source of supply for the metropolis. Four collieries in the environs of Durham 

 supply each 1,500.000 tons of fuel annually, and the nine principal seams now 

 being worked in the basins of the Tees and Tyne still contain at least eight or ten 

 milliards of tons of coal within easy reach — a quantity sufficient to last for 

 centuries at the present rate of working. The coal beds extend far beneath the 

 sea ; and statisticians, in calculating the supply of the future, have assumed that all 

 the coal within 4 miles of the coast can be got at.f The collieries, and in the 

 valley of the Tees the iron mines, have attracted a considerable population. The 

 towns press upon each other, the roadsteads and quays are crowded with shipping, 

 and even in England there are not many districts in which industry has achieved 

 such wonders. 



Yet for many centuries this was one of the poorest and least-peopled districts 

 of Great Britain — a district of permanent warfare and unexpected border raids, 

 where even in time of peace the inhabitants were obliged to be on their guard. 

 The fact that the great historical highway between England and Scotland passes 

 along the eastern foot of the Pennine range and the Cheviot Hills sufficiently 



• Smyth ; Hull, " Coal Fields of Great Biitain." 

 + Ramsay ; Eliot ; Forster ; Hull. 



