IN TFIE SOUTH OF ARRAN. 525 



boulder-clay was 1100 feet, or a little more (Aneroid barometer), but I remember 

 to have seen it 100 or 200 feet higher, and I have no doubt, patches of it may be 

 found a good deal above this, but I had not time to seek them. 



From all this it will be obvious, that the boulder-clay has not been piled up 

 in immense irregular masses, like glacier moraines, but conforms, on the whole, 

 to all the contours of the rock surface. Even in the valleys, where, of course, 

 it has accumulated in masses disproportionally great compared with those on 

 the hill faces, and where therefore the contour of the surface ceases to conform 

 strictly to that of the rock below, there are indications, in the separate beds of 

 the boulder-clay, of the modifying influence exercised upon them by the form of 

 the ground on which they have been deposited, — the line of the valley forming 

 the synclinal axis of the beds. Where wide basins exist in the valleys, which 

 is often the case above some transverse stream of igneous rock,* the boulder- 

 clay lies equally round its whole margin, and follows the slope of its banks. 



The importance of this agreement between the lines of the boulder-clay and 

 of the rock below is, that in glacier moraines, there is no such regular disposi- 

 tion of beds, and still less would such be found in the scattered droppings of 

 floating ice. 



Great irregular masses of material, resembling moraines, I only observed high 

 up on the face of the hill, between Kildonan and Benan-head ; and again, at the 

 head of Glen Cloy, where there is a huge moraine.f 



The form in which the boulder-clay beds present themselves in the burn- 

 courses is as steep slopes thinly grass-grown, — occasionally, where water oozes 

 over them, the face of the beds is steeper, more broken, and covered with con- 

 fused heaps of stones and mud. The best view of their composition is generally 

 to be got where the burn has cut in to the underlying rock, and the bank rises 

 precipitously above. 



In general character, the boulder-clay of the south of Arran is a coarse, red, 

 sandy clay, full of stones, both striated and water- worn, and of all sizes, from 

 boulders 4 or 5 feet in diameter downwards. It varies a good deal in texture, 

 being sometimes loose and gravelly, at others dense and hard, so as to stand up 

 in nearly perpendicular precipices, dotted over with projecting stones so firmly 



* One is apt to mistake mere erosions of the boulder-clay for true basins in the basement rock, 

 but where there has simply been an erosion, there is of course no such agreement as that spoken of 

 between the contours of the surface of boulder-clay and the basement rock. 



"}" I do not think this moraine has been noticed. It lies near the head of the glen, and rises 

 to a height of 800 or 900 feet above the level of the sea. Where the glen conti-acts there are, on the 

 south side, immense heaps of huge blocks of rock tumbled down in the wildest confusion, — the same 

 appears on the north side of the valley, and all the valley bottom is obstructed by heaps of gravel 

 , and stones. The cup formed by this is about half a mile long, and above, on all sides, the hills rise 

 perpendicularly to a height of 1100 or 1200 feet. Tliese moraine masses extend down to the foot of 

 G-lenDhu, more than half a mile, and in this glen, also, is some appeai-ance of smaller moraines. In 

 the lower part of the Glen Cloy moraine granite boulders become frequent. 



