1862.] JAMIESON- GLACIATION- OP SCOTIAND. 179 



extensive, is the ice-covering of the Antarctic Continent, where Sir 

 James Eoss traced a continuous vertical cliff of ice, more than 1000 

 feet thick, for 540 miles ; and detached portions were found 60 miles 

 from its main edge, aground in 1560 feet of water. 



We see, therefore, that in certain parts of the globe land-ice attains 

 a thickness at least as great as is required for the most extreme 

 cases I have adduced in this paper, even allowing that the bottoms 

 of the valleys had been as deep as they are at present when the ice 

 reached the highest scores now found on the flanking hills, which is 

 not at aU likely ; for I believe that the grinding of the ice for many 

 ages along the glens must have powerfully eroded its bed, and worn 

 the bottoms of the valleys much deeper than they were at the 

 commencement of the Glacial period, and in fact occasioned an 

 amount of denudation of the surface which has been much too little 

 allowed for. 



It may seem more probable to some, that the curious features in 

 the erosion and scoring of Knapdale may be owing to the relative 

 levels of the district having undergone considerable derangement 

 since the time at which the rocks were so marked ; and indeed, when 

 I first observed them, this seemed to myself the most likely explana- 

 tion; for although I could not, after much careful examination, 

 resist the evidence of the movement having been uphill over much 

 of the ridge, I felt much puzzled by the fact of the rocky masses on 

 the top towards Cruach Lussa being so uniformly worn on their 

 north-east exposure, while those in the bottom of the Crinan valley 

 were abraded on their east and south-east sides, indicating a move- 

 ment diverging at right angles from Loch Pyne, where there is at 

 present a vdde opening to the sea. But after studying Lochaber, 

 where the facts seem to me clearly to indicate the presence of land- 

 ice in a volume quite as extraordinary as would account for the phe- 

 nomena in Ejiapdale (allowing for erosion of the bed of Loch Fyne 

 by the long passage of the ice, as I have above suggested), I am 

 inclined to think that it is unnecessary to require any great local 

 derangement of level. 



Those who would solve the facts I have adduced in this paper by 

 means of floating ice have to show how the winds or currents that 

 moved it could have radiated from the central heights of Scotland to 

 all points of the compass, and in each district have always persisted 

 so steadily in one direction ; — how, for example, from a point in the 

 middle of Glen Spean, at the junction of the Treig, winds or currents 

 could have set out in opposite directions, and in both cases at right 

 angles to the line of movement in Glen Treig ; — how the movement 

 on one side of Scotland should have been continually from W., and 

 on the other from E., and on the north coast from S., and always 

 from the land side ; — how blocks, 15 feet long, could have been by 

 such an agency lifted up out of the bottom of a valley, and set down 

 on the bare brow of a hill hundreds of feet above their source. The 

 advocates of a debacle have, on the other hand, to show how a sudden 

 and transitory movement, even although repeated, could have lifted 

 these blocks and have worn down ragged masses of tough gneiss at 



