Correspondence — Miss C. Eyton. 95 



high ground separated from "Wasdale Crag by a watershed, Wasdale Crag (or rather 

 "Wasdaie hill), from which, I believe, most of the boulders were dispersed, is only 

 1,479 feet above the sea- level. An ice-stream, such as that supposed by Mr. CroU, 

 with a surface low enough to have received fallen blocks of granite, could scarcely 

 have been 100 feet thick on Stainmoor pass. Could such a thin layer of ice have 

 persisted in moving over the pass, so as to keep the ice-stream on the other side 

 supplied with blocks ? and in what way did the eastern ice-stream receive or acquire 

 a motion sufficient to enable it to ignore not only minor or subordinate ridges, but 

 hills in E. Yorkshire more than 1,000 feet in height? i If we suppose Mr. CroU's 

 ice-stream to have pushed the blocks from Wasdale Crag along its bed (a theory 

 which, of the two, would best accord with the fact that many of the blocks are more 

 or less rounded, and often imbedded in drift), the question arises, how could the sup- 

 posed ice-stream have acquired a power of shoving so many large boulders up a steep 

 slope nearly 1,000 feet in vertical height ? ^ 



Dispersion in different Directions. — Mr. CroU has justly remarked that ice-streams 

 may have varied their directions as their surfaces stood at different levels ; but a stream 

 of land-ice impinging on Wasdale Crag at a level which would have given it a 

 direction towards Tebay would certainly have sent it along the valley of the Lune, 

 in which valley no blocks of granite have been found. No one, I suppose, would 

 presume that a local ice-stream could have flowed up this valley so as to check the 

 glacier from Wasdale Crag. The existing configuration of the ground is likewise 

 inconsistent with the idea of local ice-streams flowing north and north-east from 

 Wasdale Crag. But the main difficulty in the way of accepting Mr. CroU's theory is 

 to be found in the fact that Wasdale Crag boulders have been carried south in the 

 direction of Kendal over a pass traversed by the Kendal road, which approaches 

 Stainmoor pass in altitude. To the north of Kendal they are found in considerable 

 numbers, imbedded in drift as well as appearing at the surface. During what stage 

 in the lowering of the 2,000 feet ice-sheet were these boulders carried southwards? 



Mr. CroU seems to think that radiating dispersion can be more easily explained by 

 land-ice than by floating -ice. That land-ice could have dispersed boulders in 

 various and often opposite directions from detached or semi-detached hills of 

 moderate elevation appears to me almost impossible. The advantages possessed by 

 the floating sea-ice (not iceberg) theory, over the land-ice theory, consist in the fact, 

 that coast-ice may be dispersed by variously- directed winds blowing off the land ; 

 by drift-currents arising from these winds ; and by ebb-tidal currents. Through these 

 mediums it may flnd its way into the courses of great tidal and other currents, and 

 these may change their directions with changes in the form of the shore or sea-bottom, 

 produced by the sinking or rising of the land, and by denudation. 



D. Mackintosh. 



THE BLUE CLAY IN THE WEST OF ENGLAND. 

 SiK, — Allow me through your pages to convey to Mr. De Eance 

 my sincere regret for having erroneously attributed the authorship of 

 his paper " On the Glacial Phenomena of Lancashire and Cheshire," 

 to Prof. Hull. I never met with the paper in full, aud therefore 

 avoided quoting its views. With regard to the thickness of the 

 blue clay near Llandudno, the reference is to a paper in your 

 November number, by Mr. H. F. Hall (not Mr. Hull, as by a mis- 

 print it appears in your correspondent's letter). My impression, on 

 reading the statement, was that it was excessive, but I would not 



1 The land-ice theory is rendered still more improhahle by the facts, that Wasdale Crag- granite 

 has found its way as far as the mouth of the Humljer ; that from a narrow neck on Stainmoor it 

 has expanded over an area forty miles in breadth (from Ripon and York to the sea-coast) ; and 

 that Liassic drift from ihe N. Yorkshire hills (over which the granite must have passed) has 

 been dispersed over the plain of York. Oryphcea incurva have been found in Boulder-clay as 

 far west as Keighley. 



2 Blocks of Permian breccia have been moved up a neighbouring slope to a vertical extent of 

 1,000 feet, and this, I think, can be sufficiently explained by the progressively upward movement 

 of coast-ice during a subsidence of the land. 



