Yol. 62.] ANNIVERSARY ADDRESS OE THE PRESIDENT. lxxxix 



Lake District with Skye. In each case the hard rocks which now 

 form those tracts must have been covered by softer or more easily- 

 denuded rocks : in the case of the Lake District certainly rocks of 

 Carboniferous age and ]N"ew-Red-Sandstone age, in that of Skye the 

 rocks into which the great intrusive masses were forced. In Skye 

 the Cuillin Hills have several summits rising over 3000 feet, and 

 the tract has been deeply trenched by streams cutting into the hard 

 rocks of the district, although the erosion in this case has been in 

 operation only during the latter part of Tertiary times. 



The Lake-District hills also rise in a few cases to a height of 

 over 3000 feet. The courses of the streams in this case, it is true, 

 are longer than those of Skye, the shortest being about three times 

 the length of the streams flowing from the Cuillins, while others are 

 longer ; and accordingly the deepening, in so far as it depends 

 upon grade, would be slower in the Lake District than in Skye. 

 In opposition to this it must be noticed that the covering of rocks 

 was probably more resistant in Skye than in the Lake District ; 

 and the intrusive masses of the former district are certainly much 

 more resistant than those of some of the highest elevations of the 

 latter, as, for example, the Skiddaw Slates of Skiddaw. If, then, 

 the Skye uplift can have been sculptured into its present condition 

 in late Tertiary times, it seems to me that the same explanation 

 applies to Lakeland ; and that if we suppose Lakeland to have 

 existed as land since, say, the end of New- Red-Sandstone times, it 

 would long ago have been reduced to a nearly-level surface by 

 denuding agencies : whereas, although the main streams have largely 

 reached base-level, this is far from being the case with the minor 

 streams, and great tracts of plateaux occur between the main valleys 

 which have hardly been touched by stream-erosion of the older rocks. 

 This erosion is still going on. The streams which course over the 

 Skiddaw Slates are turbid with sediment after heavy rains, although, 

 for a reason to be considered later, the streams which run through 

 the volcanic rocks are as a rule fairly clear even after heavy rains. 

 But even there erosion takes place during those exceptionally- 

 violent falls of rain which produce the greatest effects, witness the 

 occurrence in the Yale of St. John on August 22nd, 1749, when 

 (as described by Gilpin) a stream forced a new channel through 

 solid rock, and made a chasm at least 10 feet wide. 



Physiographically, then, the district is comparatively young, and 

 study of its physiographical features bears out the conclusions 

 attained after study of its geological structure. 



VOL. LXII. g 



