Vol. 63.] ORIGIN OF CERTAIN CANON-LIKE VALLEYS. 479 



The only statement of his views on this subject that has been 

 published is a short summary of an address delivered during 

 an excursion of the members of the Geologists' Association to 

 Birmingham in 1898, which unfortunately I had overlooked. It 

 reads as follows : — 



' Before reaching Compton Quarry a very beautiful view of Kinver Edge 

 and the surrounding landscape tempted Prof. Lapworth to develop his idea 

 of the rejuvenescence of the Severn Valley, owing to the diversion into it of 

 the drainage of the Upper Dee in Glacial times. The deepening of the main 

 Severn Valley from Coalbrookdale to Stourport, due to the increased erosion 

 brought about by the great increase in the water-supply, had permitted the 

 tributary streams entering this part of [the] main valley to cut deep gorges 

 for themselves in the lower parts of their courses. The slope of the stream- 

 beds here became more steeply inclined, and the rate of transportation in- 

 creased, resulting in a more rapid and a more differential local denudation. 

 The result is seen in the bold and picturesque scenery of the lower halves of 

 their basins in marked contrast with the more rounded and featureless country 

 farther back, which remains as yet unaffected.' (Proc. Geol. Assoc, vol. xv, 

 "1, p. 425.) 



Eeference should be made, moreover, to a paper by Mr. Gr. Maw 

 on the Severn-Valley Drift. 1 



The ' enormous concentration ' of boulders between Wolver- 

 hampton and Bridgnorth, described by Mackintosh in 1879, 2 and 

 marked on the map (PL XXXI), deserves notice. They may be 

 numbered by thousands, he states, mostly occurring between 300 

 and 500 feet above sea-level, their distribution taking the form of a 

 crescent, the convex side of which is directed south-south-eastwards, 

 its southern boundary being clearly defined. 3 The ice to which this 

 morainic accumulation was due formed a dam across the Triassic 

 region which extends south-south-eastward towards Stourbridge, the 

 natural course of the outfall when issuing from the Ironbridge canon. 

 Turning suddenly to the south, however, and keeping at first close 

 to the high land, flowing possibly between it and the ice, the stream 

 was compelled at Bridgnorth to invade Old Bed Sandstone and Car- 

 boniferous rocks for the second time, and to excavate through them 

 a straight, narrow valley of the Ironbridge type. Escaping from 

 the ice near Bewdley, it again entered and continued to follow the 

 Triassic plain. 



Mr. Walcot Gibson & Mr. C. B. Wedd, in their survey of the 

 Stoke-upon -Trent district (Sheet 123, new series), 4 and Mr. T. I. 

 Pocock and his colleagues in that of Macclesfield (Sheet 110, n. s.), 5 

 found widespread evidence of the former existence of lacustrine 

 conditions in the Cheshire plain. Laminated brickearths, deposited, 

 as they believe, during the retreat of the ice-sheet in shifting ice- 



1 Quart. Journ. Geol. Soc. vol. xx (1864) p. 130. 



2 Ibid. vol. xxxv (1879) p. 436. 



3 See also P. F. Kendall in G. F. Wright's 'Man & the Glacial Period,' 

 Internat. Sci. Ser. 2nd ed. (1893) p. 150. 



4 ' The Geology of the Country around Stoke-upon-Trent ' Mem. Geol. Surv. 

 2nd ed. (1905) p. 64. 



8 ' The Geology of the Country around Macclesfield, &c.' Mem. Geol. Surv. 

 1906, p. 91. 



Q.J.G.S. No. 252. 2 m 



