350 D. Bell — The Great Ice Age and Submergence. 



in the lower part of the Endrick valley, a few miles bej'ond the 

 south-east end of Lochloinoiifl, and at various elevations from 

 80 to 320 feet above the sea.^ This shelly Till or Boulder-clay 

 Mr. Jack attributed to the action of a glacier which occupied the 

 bed of Lochlomond after a moderate submergence had converted it, 

 for a time, into an arm of the sea. We sa}^ " a moderate sub- 

 mergence," for a little over 20 feet would suffice, as Mr. Jack 

 himself pointed out. But as a laminated clay containing some 

 marine shells and a fragment of a deer's horn was discovered in 

 the same neighbourhood at a height of 108 feet, and assumed to 

 be "in place" (which we think is open to question), Mr. Jack 

 inferred a " minimum submergence " of that amount, 108 feet. 

 This, however, he took care to say, was not to be confounded, 

 with the greater submergence in which he then believed, and 

 which he assigned to a later date. After the minor or "minimum" 

 submergence referred to, Mr. Jack's view was that " a large glacier 

 filled up the lake, covered the islands, and climbed the rising ground 

 beyond to the height of at least 320 feet," carrying up with it, from 

 the bottom of the lake, this shelly Till. 



Now, this instance evidently tells forcibly against the theory of 

 the total demolition and disappearance of marine remains as a 

 certain result of the " second glaciation." Accordingly, Dr. Geikie 

 suggests that this Strathendrick Till " belongs to a later date than 

 any of the shelly Boulder-clays " he had been referring to ; and 

 that it " appears to have been deposited by a local glacier." As to 

 time, this is quite opposed to Mr. Jack's view, which was that this 

 shelly Till preceded the " great submergence." It differs from Mr. 

 Jack's view, also, as regards the means or agency. What is meant 

 by a "local glacier"? We naturally think of one of the smaller 

 ice-sheets which continued to linger in the upland valleys and glens, 

 around the borders of the mountain districts and their gradually 

 diminishing snow-fields, after the extreme period of glaciation had 

 passed away. But Lochlomond is not in any such upland glen or 

 valley ; the bottom of it is in great part under sea-level, in parts 

 as much as 500 to 600 feet. The valley is, moreovei-, 24 miles, 

 or, with its continuation to the head of Glen Falloch, some 36 miles, 

 in length ; and there is no point nearer than the head of that glen, 

 or still farther away up Strath Fillan, among the group of high 

 mountains there, which can be indicated with any probability as 

 the place of origin of its glacier. All the striations that have 

 been observed in the district lead to that quarter. If, then, a 

 glacier 40 or 50 miles in length, and a good deal over 1000 feet 

 in thickness, — for such it must have been to have filled up the 

 lake and carried its shelly Till to an elevation of 320 feet above 

 it, — if such a glacier be called " local," it can only be in the sense 

 of not being part of a "general " ice-sheet, though apparently very 

 near it. For, when such a glacier existed in Lochlomond, we 

 may safely say that every arm of the sea all around our coasts 

 would have its glacier of corresponding dimensions, each separated 

 1 Trans. Geol. Soc. Glasgow, vol. v. 



