B. Mackintosh — Geology of the Lake- District. 447 



"worked out by Mr. S. V. Wood, jun., F.G.S.), is a very convenient, 

 if not absolutely necessary, part of a consistent explanation of the 

 sequence of events during the glacial period or periods. But it 

 becomes a question how far this ice-foot may have maintained its- 

 hold of the mountain slopes until forced to relinquish it by the 

 encroaching sea, or how far, through an amelioration of climate 

 resulting from astronomical causes, the ice-foot may have retreated 

 upwards in advance of the sea.^ It would appear evident that at 

 certain levels at least the ice-foot must have kept at a sufficiently 

 respectful distance from the sea to leave room for coast ice to act un- 

 fettered. (See Article on Shapfell Boulders.) Many, if not most of 

 the boulders which form a part of the Boulder-clay formation,'^ 

 must have radiated from, the lower (if not from some of the higher) 

 hills and slopes in various (including opposite) directions, in a 

 manner inconsistent with the pressure of a general ice-foot on the 

 sea-coast. Many of the stones have been uniformly striated on one 

 side — an effect which may have been produced under both land and 

 sea-ice, but most of the stones have been striated in various direc- 

 tions in a manner most likely to have taken place under sea-ice. 

 The stones are often the most polished and striated at a distance 

 from the mountains. Most of the stones away from elevated hill 

 slopes, where they are generally, but not always, angular or sub- 

 angular, have evidently been much rolled, and the cause or mode of 

 their attrition is not easily explained. The process may partly have 

 occurred on sea-shores now indicated by upland plateaux or slopes 

 of drift. But the comparative absence of well-rounded stones at 

 high levels necessitates our supposing that after the stones were 

 dropped into the sea by floating ice, they must have been rounded 

 by powerful currents or ground-ice, for their distribution in the clay 

 must chiefly have taken place beneath the reach of wave-action. 

 That a great part of the Boulder -clay, including its stony contents, 

 was distributed under water, is evident from the fact that where in 

 inland districts, or on the sea-coast, this clay has been newly-washed 

 by flooded streams or by waves, or where perfectly fresh sections 

 have been exposed by the tumbling down of masses, it generally pre- 

 sents the appearance of stratification, and even false-bedding, as much 

 as the nature of the deposit could have allowed it to receive or retain.^ 

 Over an area extending from Long Sleddale on the E. to Coniston 

 Old Man on the W., and reaching at least as far north as Amble - 



^ The character and mode of occurrence of the blue clay of the N.-'W. of England, 

 but especially of the West Riding of Yorkshire, (see Paper- on the West Eiding 

 Drifts in forthcoming Proceedings of the West Eiding Geol. Soc, noticed in Geol. 

 Mag. of last June,) suggests another question, namely, whether the submergence 

 commenced before the arrival of a comparatively mild climate, followed by a second 

 sub-glacial period. This, of course, supposes that the astronomical may have been 

 suflQcient to neutralize the geological causes of climatal revolutions. 



2 These boulders are not merely surface-blocks, but are often deeply imbedded, and 

 most numerous towards the base of the deposit. 



3 Mr. Hull and Professor Eamsay both arrived at the conclusion that the two 

 Boulder-clays of Lancashire were stratified. Mem. Lit. Phil. Soc, Manchester, 

 for 1863-64. 



