CXX PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May I906, 



Valley, Ullswater, and others. Where these valleys have subsequently 

 been modified by erosion along shatter-belts the modified parts are 

 marked by their straightness, as, for instance, that part of the 

 Duddon which lies between Wallabarrow and Birks Bridge. 



In some cases the lower parts of valleys which in higher parts 

 run along shatter-belts are marked by crooked courses, as in the 

 case of the Duddon and Grasmere valleys. In these instances the 

 lower portions are in rather soft rocks, or at any rate in very 

 well-jointed rocks, which were somewhat easily eroded, and where, 

 indeed, the major shatter-belts are often replaced by hosts of minor 

 ones. 



I lay special stress on the straightness of the valleys along lines 

 of shatter-belt, as the absence of overlapping spurs in such valleys 

 has been used as an argument for the deepening of these valleys by 

 ice. Whether that deepening be by ice or water, this straightness 

 is not due to the eroding agent, but to the rock-structure. 



The width of the valleys and the occurrence of wide alluvial floors 

 at their bases shows that, if eroded by water, they established their 

 base-levels at a remote date ; and it may be argued that this being 

 so, the hanging valleys ought to have established their grades. 

 That they will do so some day under present conditions is clear ; 

 but if the amount of erosion carried on by these streams, on rocks 

 not occupied by shatter-belts, is insignificant when compared 

 with that of the streams which do run over shatter-belts : then, 

 notwithstanding the time which has elapsed since the main streams 

 established their base-levels, that interval may be but a fraction of 

 the whole time required for the adjustment of the grades of the 

 tributaries. 



It must be noted also that they are, by degrees, adjusting their 

 grades. Sty-Head Beck, for instance, has cut a good deal back from 

 Taylor-Gill Fall, and is raising its bed at the bottom of that fall 

 by building up a delta-fan ; and the same is the case with the other 

 hanging valleys in varying degrees. 



We may note further that, where tributary streams are themselves 

 along shatter-belts, they do not occupy hanging valleys : as witness 

 the various streams which descend into the Bothay above Winder- 

 mere, from Fairfield and Red Screes. 



The importance of hanging valleys is apt to be overestimated 

 as the result of casual inspection. Some valleys which appear to 



