610 the howgill fells and their topography. [nov. i909, 



Conclusions. 



We may now sum up our results by stating that the Howgill 

 Fells are a monoclinal block, formed of Silurian rocks which have 

 been glaciated by their own ice. The erosive effects of the ice 

 have been chiefly exerted in widening the valleys, by truncating 

 the spurs and forming conchoidal scoops on the concave sides. 

 The amount of deepening is small, as indicated by the slight 

 difference of grade at the junctions of the tributaries and the main 

 streams which is measured by only a few or at the most by tens 

 of feet, the latter in the case of the junctions of the streams on 

 the west side of the Fells with the River Lune. Accordingly, the 

 hanging of the tributaries is insignificant. The great hanging 

 valleys have been determined by the capture of the head-waters 

 of the northward-flowing streams by the more steeply graded streams 

 flowing southwards or south-westwards, although these captures 

 have been partly aided by glacial action. 



The rarity of roches moutonnees and ice-scratched surfaces is a 

 noticeable feature, but it must be remembered that the places 

 favourable for their preservation are chiefly masked by vegetation. 



The comparatively feeble action of the ice may, of course, be 

 largely due to its inability to obtain free outlet from the Fell 

 country, owing to resistance and interference of the Lake District 

 ice on the one hand and of the Wild Boar Fell and Baugh Fell ice 

 on the other ; and we have no desire to generalize, as to the action 

 of ice in other regions, from our observations in this limited tract. 

 We think, however, that our work may prove useful, as showing 

 the varied effects of glaciation in a district of practically homo- 

 geneous rock, where there is every gradation from the ordinary 

 valley-outlines of a water-eroded tract of moel type to those of a 

 marked U-shape, such as are seen at Cautley where ice has exerted 

 a very considerable influence. 



EXPLANATION OF PLATES XXVIII-XXXI. 



Plate XXVIII. 



The Howgill Fells, seen from Ash Fell. The cultivated valley in the middle 



distance is Ravenstonedale. Notice the gentle northerly slope, increasing 



in steepness as it approaches the valley (see also PI. XXXI, fig. 2) and 



the steep scarp facing southwards. 



Plate XXIX. 



Map of the rivers of the Howgill Fells, on the scale of a mile and a half 



to the inch. 



Plate XXX. 



Map of the glaciers of the Howgill Fells, on the scale of a mile and a half 

 to the inch. 



Plate XXXI. 



Fig. 1. Section showing the thalweg of the beheaded Artlegarthdale and its 

 tributary valleys. 

 2. Section along the watershedding line west of Bowderdale. 

 [Scales: -vertical, 6 inches = 1 mile; horizontal, 3 inches = 1 mile.] 



