Correspondence. 523 



sea. Supposing, then, the general contour of the land to have been 

 in the main, what it now is, previous to that submergence, are not 

 almost all the phenomena described by Mr. Mackintosh precisely 

 such as we might expect to have been produced by such a subsidence 

 as would permit the sea to flow into the existing valleys of Wales ? 

 Are not the traces ^ of sea-action, which he finds, more consistent, in 

 short, with the theory of a temporary submergence of land already 

 modelled into nearly its present contour, than with that of the eating 

 out of such an intricate network of "fiords" by the gradual opera- 

 tion of the sea upon an elevated and rocky land ? How, again, I 

 would ask, can Mr. Mackintosh possibly explain the formation of 

 such a long tortuous gorge as that, for example, through which the 

 river Alyn flows for some miles above Gresford ? Taking that gorge 

 in connexion with the ridge of Drift-gravel, at the east of G-resford and 

 Wrexham (the old sea beach, perhaps,) through which the river cuts 

 its way, we have as clear a case as may be of river-action. And if 

 there, why not in other similar gorges throughout the country ? 

 Even Mr. Mackintosh will scarcely argue that the long alternations 

 of tunnel and deep cutting, through which so many of the limestone 

 rivers of Yorkshire find their way, were made for them by the sea. 



I am, Sir, yours faithfully, 



William Pukton. 

 Stottesden Vicarage, Bewdley. 



To the Editor of the Geological Magazine. 



Sir, — Mr. Hull's letter on the " Eiver-denudation of Valleys," 

 in your number for October, is valuable as again calling attention 

 to a very puzzling fact, which I agree with him in thinking has not 

 yet received a perfectly satisfactory explanation. I pointed out some 

 time ago two cases in North Staffordshire of a valley crossed by a 

 watershed, exactly like the instances described by Mr. Hull, but on 

 a larger scale. ^ 



It is not, however, my intention to attempt a solution of this 

 knotty problem, but to point out one sentence in Mr. Hull's letter, 

 so plausible, and, at the same time, so illogical, savouring of the 

 post hoc ergo propter hoc, that I hope the author will excuse me if I 

 show the flaw in his reasoning. 



The sentence is, " It is less incredible (to say the least of it) to 

 assume the agency of the sea in the formation of these valleys (or 

 parts of them), which we know was there, than that of a stream of 

 which there is no trace." 



The argument stated formally runs thus : 



We know that the sea has been over the ground now occupied by 

 the vale of Todmorden. 



1 Except, indeed, his supposed instances of " sea-worn summits of hills," about 

 which I confess I am rather sceptical. 



2 See the Memoir of the Geological Survey on the country round Stockport, 

 Macclesfield, Congleton, and Leek (p. 13). 



