868 J. GEIKIE ON THE GLACIAL PHENOMENA 



Skye and N. ITist differ conspicuously. ' There are very few erratics 

 in the Outer Hebrides ; very few W.Uist erratics in Skye. Probably 

 the movement of ice afloat coincided with that of tides, and was 

 from the north rather than from the south. 



Mr. Belt thought that the evidence on which Mr. Geikie had founded 

 his conclusion that the ice that had glaciated the Outer Hebrides 

 came from the south-east was unsatisfactory, and that some of it 

 actually pointed to the opposite opinion. That more till had been 

 left on the west sides of the islands than on the east was in- 

 consistent with the idea that the ice had come from the latter 

 direction. During the increase and greatest extension of the ice it 

 would polish and score the rocks below it, and it was during its 

 retreat that it would leave behind it the detritus it had gathered 

 into its mass. As it melted back, the mud and stones would be 

 deposited on slopes opposed to its course, as there the water issuing 

 from the retreating glacier would be pounded back ; whilst on the 

 slopes coinciding with its flow the water would find a free outlet, 

 and carry away the mud, as it does now in the Swiss glaciers. 



The hills of Skye lay directly in the course of the supposed flow 

 of ice from the mainland, and their rocks should have been largely re- 

 presented in the boulders of the Outer Hebrides on Mr. Geikie's theory, 

 but they were entirely absent. Even if the ice at one time passed 

 completely over the Outer Hebrides, a time would come in its retroces- 

 sion when it ought to have left its terminal moraine there, and in this 

 the rocks of Skye should have abounded. Their absence seemed to 

 be fatal to the theory brought before them. 



He objected to the notion that the lower portion of the ice-flow 

 could have moved at right angles to that invading and overflowing 

 the Hebrides. If there was an outlet for the deepest portion of the 

 ice to the south-west, there must also have been one in the same 

 direction for the upper portion, and no reason would exist for the 

 persistent flow of the ice over the whole of the Hebrides in a north- 

 west and south-east line. 



The Duke of Argyll referred to the glacial phenomena of the 

 Inner Hebrides and the mainland, and said that from these he was 

 led entirely to disbelieve in the theory of an ice-sheet, not because 

 he did not believe in a " glacial period," that is, that there had 

 formerly been a great extension of ice where now there is none. 

 All the phenomena he had seen could be accounted for by the action 

 of glaciers and of floating ice. All over the Highlands there were on 

 the hills, up to 1400 or 1500 feet, perched boulders, not rounded or 

 scratched, proving, he thought, a submergence to that extent. 

 These, he thought, could not be explained by an ice-sheet. They 

 generally rested on exposed knolls and prominences, and could only 

 be accounted for by assuming the agency of ice-rafts loaded with 

 rocks. Now if there were a gradual rising and sinking of the land, 

 the whole surface would be glaciated. He thought that a Palseo- 

 crystic sea would give all the conditions required for the glaciation 

 of the Highlands. We have no proof of ice being able to walk up 



