Vol. 62.] ANNIVERSARY ADDRESS OE THE PRESIDENT. CI 



If the uplift be considerable and recent, the elevations may be 

 relatively great, even when the rocks are not very resistant ; thus 

 the fairly-soft Carboniferous rocks of the Pennine Chain rise to a 

 height of 2930 feet on Cross Fell, less than 300 feet lower than 

 Scawfell; while the heights of the English Jurassic rocks nearly 

 touch 1500 feet, and those of the Cretaceous rocks in several places 

 approach 1000 feet. 



It is in the middle age of an uplift, when denudation has produced 

 its most marked contrasts between uplands and lowland's, that the 

 effects of the relative resistance of rocks are most marked. 



These facts are, of course, well known. I merely refer to them 

 because they are too often overlooked, in the case of the elevations 

 of our own island. 



The slight difference between the heights of Scawfell and Skiddaw, 

 and especially the slight change in the elevations of many of the 

 slopes where they pass from volcanic rocks on to Skiddaw Slates on 

 the one hand, or on to the Upper Slates on the other, seems to me 

 to be an additional argument in favour of the youth of the district, 

 speaking in a geological sense. 



Again, the general elevation of the tract of Upper Slates of the 

 Howgill and Kirkby-Lonsdale Fells, when contrasted with the 

 comparatively-low ground occupied by these slates in the southern 

 part of the Lake District proper, is explicable on the view that a sub- 

 sidiary uplift has taken x^lace in the Howgill Fells. The low ground 

 occupied by the Upper Slates of the southern part of the district 

 receives its explanation in the fact that they lie almost entirely at 

 some distance from the axis of the uplift of the dome ; when they 

 approach that axis, namely at the head of the southern JBorrowdale, 

 we find the fells formed by these rocks reaching their greatest 

 height in the area of the main dome. 



The softness of the Skiddaw Slates has produced its effect, not 

 in the general lowering of the watersheds as compared with those 

 of the volcanic tract, but in the more rapid erosive work of the 

 tributary streams coursing down the valley-sides and cutting away 

 the plateaux, thus originating the sharp peaks of the Skiddaw area, 

 and the scarcity of plateaux as compared with the volcanic tract. 



It is the greater uniformity of the rocks of the Skiddaw tract 

 than of those of the volcanic district which causes the most marked 

 contrasts. The harder lavas, coarse breccias, and flinty ashes of 

 the latter tend to stand out as cliff=i, while the more vesicular 

 lavas and softer ashes are worn away. The flinty ashes of the 



