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an elevated platform of transition rocks. The windings are often 

 so extreme, that the river returns after a course of seventeen miles 

 in one instance, and nearly as much in two others, to within a di- 

 stance of a few hundred yards of the spot it passed before; wearing 

 away on either side the base of the ridge-shaped isthmus that sepa- 

 rates the curves, and inclosing a peninsula of elevated land five or 

 six hundred feet high ; but sloping towards the bottom of the curves, 

 where it is strewed with boulders, left there, the author presumes, 

 by the river as it gradually deepened its channel and extended its 

 lateral curvature. 



The valley of the Meuse near Givet, offers, through a great di- 

 stance, a number of similar windings, and the same thing is seen at 

 intervals in many of the other rivers of that country. Parts of the 

 Seine below Paris, and the valley of the Wye between Hereford 

 and Chepstow, are examples nearer home. 



Valleys which like these twist about in the same regular curves 

 as the channel of a brook meandering through a meadow, can, ac- 

 cording to the author, only be accounted for by the slow and long- 

 continued erosion of the streams that still flow in them, increased 

 at intervals by wintry floods. To attribute them to a transient and 

 tremendous rush of water in the main direction of the valley, is in 

 his opinion impossible. He contends that whilst these valleys were 

 slowly excavated, other rivers could not have been idle during the 

 same protracted period ; but will have produced likewise an amount 

 of excavation proportioned to their volume and velocity, and the 

 nature of the rocks they flowed over. In the examples quoted, 

 the rocks are mostly hard transition strata, yet the valleys are wide 

 and deep. Where softer strata, as sands, clays, and marls, were 

 the materials worked upon, the valleys excavated may be expected, 

 as they are found to be, far wider in proportion to the volume of 

 water flowing through them. The comparative softness of the ma- 

 terials also, by accelerating the lateral erosion of the stream, will 

 have multiplied the shiftings of its channel, and reduced their sum 

 with greater certainty to one average direction. Hence the deeply 

 sinuous valleys are only found penetrating the more solid rock 

 formations. The author thinks that a certain subdued velocity in 

 the stream is also necessary to produce this result; and, therefore, 

 in mountainous districts, where the torrents and rivers are most 

 rapid, their course is nearly straight ; thus confirming the author's 

 opinion, that extreme curvature of channel can only be produced 

 by a slow and comparatively tranquil process of excavation. 



PRINTED BY RICHARD TAYLOR, 

 RED LION COURT, FLEET STREET. 



