Edward Merrick — The River Tyne Drainage Area. 357 



line of geological elevation may not represent the actual position of 

 the rocks in time past, but in Tynedale the geological elevation and 

 former position of the Millstone Grit are identical, for the fell tops 

 are capped by it, proving that it once crossed the valleys between 

 them. Denudation in the Weald has cut to a greater depth than in 

 the Tyne area, and as it occurred there in post-Cretaceous times 

 the denudation here may not have acted continuously since the 

 Permian period ; in fact, it may be quite young. On the other hand, 

 Tynedale may be regarded as containing better weather-resisting 

 rocks than the Weald. Some time will have to elapse before Cross 

 Pell is replaced by a river and the Tyne Valley becomes a synclinal 

 mountain (Fig. 9c). 



A noticeable feature of the Tyne between St. Peter's and Hebburn is 

 that it flows between two rocky banks for a little distance ; elsewhere, 

 though rock be exposed in its bed or on one bank, the other bank is 

 generally composed of superficial deposits. A little further east the 

 Tyne passes the outlier of the Permian escarpment on Tynemouth 

 cliffs and then joins the sea. 



The Ouseburn in .Tesmond Dene and the Burn at Newburn have 

 this rocky feature also, but not the Team nor the Derwent. The 

 rocky and narrow valleys are cut nearly at right angles to the strike 

 of the strata, while the other and wider valleys are nearly parallel 

 with the strike. These rocky streams are also at a less depth below 

 the restored surface of the land than the other streams. This nearness 

 to the original surface brings about the following effects (which are 

 independent of the recent changes in sea-level) : — 



1. An example of stream action found in the collecting areas of its 

 tributaries. 



2. An appearance of youth through less depth of erosion. 



3. An appearance of age, because the Tyne is tidal here and at its 

 base-level of erosion (for the present moment). 



This part of the river bears comparison with the rivers from the 

 Weald cutting through the Chalk escarpment and then running either 

 into an area of Tertiary rocks or the sea. 



Coincidence with old lines of weakness, etc. 



The following examples show the relationship between the present 

 land surface and older features : — 



1. The Pennine Fault through being pre-Permian and post-Triassic 

 is an old line of weakness and motion. It has produced part of the 

 western watershed to the Tyne. 



2. The present-day watershed from Cross Fell to Cleadon lies above 

 the pre-Carboniferous ridge which was inferred by Mr. J. G. Goodchild 

 and given in position in Mr. Jukes-Browne's Physical Geology. 



3. The Carboniferous strata below the Millstone Grit in the Tyne 

 Valley are collectively thicker than those on the southern watershed. 



4. That this watershed follows the general direction of the junction 

 plane between the Coal-measures and the Permian strata is shown in 

 a section drawn by Messrs. Wood, Taylor, and Marley from Hownes 

 Gill to Monkwearmouth. There is also a slight increase of slope of 

 the junction plane near the coast. 



