284 GENERAL OBSERVATIONS. 



SM eep through part of a hill. In a similar way, the Derwent, which 

 rises in the moors between Whitby and Scarborough, does not run 

 down to the sea by the opening at Scalby, but passes on between steep 

 banks to Ay ton, and into the vale of Pickering; and on approaching 

 the chalk strata, it does not turn to the left in the direction of Filey, 

 which seems the most natural and easy passage, but flows round the 

 foot of the Wolds, by Malton and Howshara, finding its way between 

 banks that are higher and stronger than the obstacles which opposed 

 its progress in the other direction. In such cases, it is quite clear, that 

 the streams have neither cut their channels, nor deposited the alluvium 

 that covers the principal part of the valleys through which they pass. 

 Many of the valleys, indeed, bear marks of their having been formed 

 or modified by the flowing of waters ; yet not by the flowing of their 

 own little streams, but by the waters which once covered the whole 

 of our rocks; and which in retiring have washed away vast portions 

 of the more loose or exposed parts of the strata, and employed the 

 materials, thus obtained, in forming the alluvial covering. 



In like manner, the river Tees, and its tributary streams, cannot 

 be conceived to have given the fronts of the Cleveland hills their 

 shape, and formed the deep recesses between them. The Leven, 

 which collects a great part of the streams that flow from them, 

 makes its way through deep beds of alluvium, which it cannot have 

 deposited ; but though it has deepened its channel, by wearing away 

 the soft alluvial beds, it has made little impression on the sandstone 

 strata, in the few places where it reaches them. To ascribe to cur- 

 rents so limited in their operations, effects of such magnitude as the 

 shaping of mountains, and the formation of extensive valleys and 

 plains, is altogether unphilosophical. 



Besides, what shall we say of those valleys in which there are no 

 streams, of which we have so many in our oolite hills and chalk hills ? 

 And what shall we say of the subterraneous channels of the becks 



