82 



It seems more natural to suppose that the precipitation would 

 have been much greater then than it is at present, and would have 

 been far more abundant in winter than in summer, and that even 

 in summer it would have taken the form of snow rather than of 

 torrential rains, which must have frozen on the ground. And if 

 glaciers covered the downs it would have been the sub-glacial 

 streams of August that hollowed out the coombes. 



Mr. Lamplugh thinks that the growth of ice-sheets has depended 

 far more on the amount of snowfall than on the severity of the cold, 

 and he adds the following valuable remarks. 



Taking it as granted that an unbroken ice-sheet extended from 

 Scandinavia S.W. over the greater portion of the British Isles and 

 that its surface, in the northern pans of the North Sea and Irish 

 Sea reached an elevation of at least 1,000 feet, and probably very much 

 move, above present sea level, this must have had a considerable 

 effect upon the snowfall of the region. The evaporating water- 

 surfaces of the Baltic, North and Irish seas would have been 

 obliterated, but there would have been provided a high-level condensa- 

 tion area for the moisture-laden currents from the North Atlantic. 



These would infringe upon a plateau higher than the present 

 land, and with a surface temperature never above 32 0 Frit. Hence 

 a large proportion of the total precipitation would fall within a 

 limited distance of the ice border. We should then have a very 

 considerable addition to the mass of the ice-sheet towards its border, 

 independently of any flow from the north. 



This tendency towards marginal accumulation would be counter- 

 acted by the greater freedom of movement on free ice-borders fronting 

 the sea. — 50. 



Thus, it would appear that, apart from the continuance of any 

 glacial flow from the north, this marginal accumulation of ice on 

 frozen land would steadily advance towards the south, fed by moist- 

 ure-laden currents, until it broke off, and floated away in the sea. 



In 1888 I visited the Scilly Isles, and found and now show some 

 scattered pieces of flint and even a few that are worked, and I con- 

 cluded that they had been brought by ice from Ireand. In a 

 Geological Memoir, by George Barrow, of the Isle of Scilly, pub- 

 lished in 1906 are the following statements: — 



" Rocks of a distant origin and chalk flints were found on St. 

 Martin's, 160 feet above O.D. After flint the most common pebbles 

 are a reddish brown sandstone, often striated''' (? Sarsen). — 51. 



" There are also greensand chert, granite derivatives from the 

 S.W. of England, fragments of kellas, and igneous materials. The 

 flint and chert resemble those in the subangular gravels of Haldon 

 in Devon, and their occurence suggests an easterly origin. 



"That these stones (on Tresco found at the height of 105 feet) 

 were brought by glacial agency admits of little doubt. It is proved 

 by their distribution and their strise. They were carried by floe-ice." 



50— Glac. Mag., i., 231. 

 51 — pp. 2i, 22, 23. 



