1865.] JAMIESON LAST CHANGES IN SCOTLAND, 167 



througli it, "without any regular arrangement. The surfaces of the 

 stones are often scratched and worn like the subjacent rock ; and this 

 is the case alike with the large boulders and smaller pebbles, pieces 

 of the size of the finger-nail being frequently well marked if of a 

 fine-grained quality ; and it is on stones of this kind, such as clay- 

 slate, serpentine, and limestone, that these appearances are best dis- 

 played. When the stone is of an elliptical form, the scratches run 

 lengthways along it ; they are not confined to one side, but often 

 cover the whole surface ; and it is worthy of notice that the scores 

 on the boulders, as they lie imbedded in the clay, often coincide in 

 their direction with the furrows on the solid rock beneath*. The 

 stones themselves are of such kinds as occur in the direction towards 

 which the ice-worn faces of the rock look ; the scores on the sub- 

 jacent rock point towards the mineral masses whence the boulders 

 have come. Now all this shows that the boulder-earth, with its 

 imbedded fragments, was pushed along by the same agent that 

 scored the rocky bed on which it lies. Thus on the top of the 

 sandstone -hills that form the south end of the island of Bute, we 

 find the ice-worn debris of the mountains of Argyleshire ; in the 

 boulders of Inverness we find samples of the rocks that occur along 

 the line of the Caledonian Canal ; and at Aberdeen we get spe- 

 cimens of all those that are to be met with in the Yalley of the 

 Dee. The materials of this boulder-earth have therefore set out 

 from the same regions as the striae on the rocks, namely, from the 

 lines laid down on the map (fig. 1), and as they moved along they 

 have mingled with the debris of each successive formation they 

 passed over. 



Underneath the present glaciers of Switzerland there is found a 

 bed of mud mixed with stones, which Agassiz describes as la couche 

 de houe, or la houe glaciaire (see ' Systeme Glaciaire,' p. 574), being 

 the stuff that arises from the triturating action 'of the ice on its 

 rocky bed; and Dr. Hooker, in his Himalayan Journals, remarks 

 that " the action of broad glaciers on gentle slopes is to raise their 

 own beds by the accumulation of gravel, which their lower surface 

 carries and pushes forward." The boulder-mud of Scotland (or 

 Till as Sir Charles Lyell calls it), I therefore take to be the stuff 

 resulting from the triturating action of the great fields of ice which 

 overspread the country during the Glacial period. It lay beneath 

 the ice- crust, and was compressed and pushed along by it, and 

 accordingly its features correspond with this notion. It is generally 

 hard and compact, as if it had been subjected to great compression. 

 It is an azoic mass, destitute of all trace of contemporary animal or 

 vegetable life. The beds that contain remains of sea-shells and 

 other marine organisms belong, so far as my own observation goes, 



* That is to say, supposing the scores on the subjacent rock point north- 

 west, then the longer axes of the pebbles in the clay generally pomt in the same 

 direction. In the bed of the Lothrie bui-n, near the village of Leshe in Fife, 

 immediately above Balhngall Mill, I observed a fine example of paraUeHsm 

 of the scratches on a number of large boulders — the direction being about 

 W. 10° N. 



