Pre-glacial River Valleys. 



531 



below. This may be well seen at Durham on the 

 Wear. 



' The pre-Grlacial valley,' says Mr. H. H. Howell, in 

 a letter which I quote, ' runs nearly north and south 

 from Durham to Newcastle. The river Wear, instead 

 of following this old valley, meanders about, winding 

 in and out of it, and at Durham cutting right across 

 it, and passing into the sandstones of the Coal-mea- 

 sures, through which it has cut its way in a narrow 

 gorge. At Chester-le-Street, half-way between Durham 

 and Newcastle, the river Wear leaves the course of the 

 old valley altogether, and, turning to the east, makes its 

 way to the sea at Sunderland, passing principally 

 through sandstones and shales of the Coal-measures, and 

 cutting through the Magnesian Limestone, just before 

 entering the sea.' 1 



It is for this reason that coal-miners in Northum- 

 berland and Durham, while mining a bed of coal, some- 



FIG. 105. 



1. Boulder-clay filling a valley. 2. Coal-measures with beds of coal. 



times find it crop up deep underground against a 

 mass of Boulder-clay that fills an ancient rocky valley, 

 of which the plain above gives no indication. 



Again, if we examine the channels of other rivers 

 in the south-east of England, we find that in places the 



1 See Transactions of the North of England Institute of Mining 

 Engineers,' voL xiii. pp. 69 to 85, especially the Map at p. 69 and 

 the section p. 77. 



M 11 2 



