Note 282 — Chapter XXIX · EVIDENCE FROM BURIED RIVER CHANNELS OF A CONTINENTAL PERIOD IN BRITAIN.[279]

Mr. Milne Home has advanced, in his “Estuary of the Firth of Forth,” p. 91, the theory that this trough had been scooped out during the glacial epoch by icebergs floating through the Midland valley from west to east when it was submerged. The bottom of the trough, be it observed, at the watershed at Kilsyth, is 300 feet above the level of its bottom at Grangemouth; and this Mr. Milne Home freely admits. But he has not explained how an iceberg, which could float across the shallow water at Kilsyth, say, 100 feet deep, could manage to grind the rocky bottom at Grangemouth, where it was not less than 400 feet deep. “The impetus acquired in the Kyle at Kilsyth,” says Mr. Milne Home, “would keep them moving on, and the prevailing westerly winds would also aid, so that when grating on the subjacent carboniferous rocks they would not have much difficulty in scooping out a channel both wider and deeper than at Kilsyth.” But how could they “grate on the subjacent carboniferous rocks” at Grangemouth, if they managed to float at Kilsyth? Surely an iceberg that could “grate” at Grangemouth would “ground” at Kilsyth.