194 MR. R. B. OLDHAM ON THE [May I9OI, 



divided into three portions, that of Skiddaw on the north — which 

 lies outside the present discussion — of the Helvellyn-Shap Fell ridge, 

 and of the Sea Eell-High Kaise ridge ; the latter being partially 

 interrupted by the Stake Pass, as is the Helvellyn-Shap Fell ridge 

 by the Kirkstone Pass. In each of these two masses, considered 

 separately, the drainage can be better regarded as diverging from 

 an axis than from a point. In the western mass, the drainage is 

 more radial : we have it in Borrowdale flowing northward ; in 

 Euttermere flowing north-westward ; Ennerdale towards the west ; 

 Wastwater to the south-west ; while a ridge runs southward to the 

 Old Man of Coniston, and breaks the drainage into smaller valleys 

 flowing south-westward and south-eastward. On the opposite side 

 of the Dunmail Raise the drainage is palpably axial : there are the 

 two large valleys of Ullswater and Haweswater flowing north- 

 north-eastward, and a number of smaller valleys drain the southern 

 slopes of this ridge. 



These two masses of high ground are separated by the gap of the 

 Dunmail E-aise ; but this gap is in no way, or at most to a very 

 slight degree, due to lessened elevation, the whole, or nearly the 

 whole, of the depression being due to an excess of erosion. We may 

 consequently leave it out of consideration in determining the 

 original form of the elevated mass, or more properly that which it 

 would have assumed had there been no denudation. Considered in 

 this way, we find that it is not a dome, but a barrel-vault, terminating 

 in the west in a semidome ; to the east the axis continues beyond 

 the area of the Lake District, and its further continuation need not 

 be considered. 



The recognition of an axis, as opposed to a centre, of elevation, 

 does away with the necessity of attributing the elevation to the 

 intrusion of a laccolite, but does not preclude the possibility of this 

 cause, for there is no necessity for the symmetry of a laccolite to be 

 radial and give rise to a dome- shaped elevation, though such is 

 doubtless the most common form. A weightier objection is to be 

 found in the history of the Dunmail Valley ; the elevation of the 

 hills evidently took place slowly, for a period sufiicient to allow the 

 river to lower its bed at least 2000 feet before elevation was able 

 to master erosion. So slow and prolonged an elevation appears to 

 be incompatible with its being caused by the intrusion of a laccolite, 

 a cause which is likely to produce a comparatively rapid elevation 

 of the surface. 



Another point in which the explanation of the Dunmail Raise 

 here offered comes into contact with previously proposed explana- 

 tions of the origin of the surface- features of the Lake District, is 



Windermere Valley, a river which was interrupted and divided at an earlier 

 period than that of the Dunmail Raise. 



The Stake Pass may similarly mark the course of a river which crossed this 

 area from the north, flowing along what is now the Borrowdale valley ; but of 

 this I cannot speak, as I have not seen the pass. 



