158 Mackintosit — The Sea \. Rivers. 



dry. All the water coining from another finds its way through a 

 small spout on the roadside ; and although the stream from the third 

 may not make so great a display of its denudating power, in the shape 

 of an artificial cascade, it may be quite as large, and, in the eyes 

 of subaerialists, perhaps as able to scoop out a combe as the last- 

 mentioned. But these "dismal hollows "^ cannot by any straining 

 of the subaerial hypothesis be satisfactorily explained. All the facts 

 are against rain, frost, and streams. The slopes are protected by a 

 thick and varied covering of vegetation. Their dryness is quite 

 remarkable ; and to appeal to the very few small springs, scattered 

 at long intervals along the base of the hills, as denudating agents, 

 would be out of the question. I do not see how the conclusion can 

 be evaded, that these deep hollows point out some of those parts of 

 the western shore of the Malvern Straits which were most exposed 

 to the fury of storms, or the sweeping action of currents. As 

 the geologist surveys these hollows, he may at the same time look 

 across the old bed of the Severn Sea ; and recognize in the distant 

 Cotswold escarpment the counterpart of the coast-line on which he 

 stands, with headlands on the one side corresponding in form to 

 headlands on the other, and combe answering to combe, where 

 once " deep called unto deep." 



Denudation of the Longmynd Valleys. — From the dry valleys of the 

 Malvern Hills we may find an easy transition to the deep " gulleys " 

 of the Longmynd, in Shropshire. I am not aware of any spot 

 in South Britain to which the subaerialist might more readily lay 

 claim ; but even here I think it can be shown that the streams were 

 originally usiu'pers of the valleys, or that the valleys made the 

 streams, and not the streams the valleys. From the high and com- 

 paratively level plateau of the Portway, the main valleys in their 

 general course cut across the strike of the nearly perpendicular 

 strata, towards the pass of Church Stretton, which bounds the 

 mountain on the east. Their directions could not, therefore, have 

 been determined by comparatively yielding strata. The valleys in 

 many parts are very winding, and they could not, therefore, have 

 been excavated by a stream running down so steep an inclination as 

 would have been necessary to give sufficient excavating power ; for 

 in proportion to the slope in the bed of a stream, must be its 

 tendency to flow in a straight line.^ In the Longmynd, the smaller 

 streams run in nearly all directions, irrespective of hard and soft 

 rocks, and the hollows they traverse are often continuations of inter- 

 vening cols. Many hollows are dry, or are moistened by a rill so 

 choked with vegetation as to render it scarcely visible. Several 

 streams flow down into the deep valleys along a general inclined 

 plane, without any depression, beyond a few inches, to mark their 

 course ; and these are as large as streams which in other places 

 traverse comparatively deep and wide gulleys. The upper ends of 

 some valleys (Oakham Dingle for instance) are large and combe- 



^ Camden long ago called a hollow in this neighbourhood the Dismal Hollow. 

 2 See Mr. Fergusson's Paper on the Ganges, in Quart. Journ. Geol. Soc, vol. xix., 

 Aug. 1863. 



