IN THE SOUTH OF ARRAN. 537 



particular portion of the clay which is stratified or shell-bearing, and cannot be 

 held to exclude the great mass of the beds, which, in their heterogeneous stiff 

 clay mixed with striated stones, present — if not in high development, yet beyond 

 a doubt — all the characteristics of true boulder-clay. If parts of the beds, then, 

 must be classed undoubtedly as boulder-clay, the whole must be so called, and the 

 elevation of mere stratification and the presence of shells into crucial tests of 

 Avhat is not boulder-clay must be rejected. But, besides this, these beds belong un- 

 questionably to the glacial period, as is proved by the striated surfaces of the 

 rock and of the stones, and by the boreal character of the shells. Now, failing 

 any evidence of the submergence of Arran during the glacial epoch, we may con- 

 clude that boulder-clay must have been deposited on the island ; and unless it 

 were true, as it is not, that the boulder-clay has been entirely remade, and that 

 the existing beds are the mere wrecks of that deposit — then these must just be 

 the boulder-clay beds of the glacial period. 



Such, then, are the facts here presented to us ; and with these facts before us, 

 it is obvious that we have, to some extent, a record of the history of the land. 

 How far can we decipher the record ? 



Let us start from what we know. In geologically recent times there has been 

 a glacial period. The existence of roches moutonnees^ of striated surfaces and of 

 scratched boulders, proves the action of ice on the land. The presence of marine 

 shells and of water deposits is evidence of the submergence of the land to a con- 

 siderable depth. Its present state implies its re-elevation. Of these phenomena 

 enough at least exists in the south of Arran — in the boreal shells, the striated 

 stones, and the hard chaotic clay — to justify the belief that this district formed 

 no exception to the general condition of the country ; that any differences here 

 are due to local circumstances ; and that we may fairly bring the general infor- 

 mation gathered elsewhere to eke out our knowledge of this district. Assuming, 

 therefore, that in Arran, as elsewhere, the land was gradually covered by ice, let 

 us try to conceive the result. 



At first snow w^ould accumulate on the hill tops, creeping thence as glaciers 

 down the valleys. As it grew in depth, it would spread further and further on 

 the slopes till the whole land was swathed deep in ice. The fact that in our 

 country all the rock surface at all elevations, with mere local exceptions, is 

 striated, indicates such an existence, not of glaciers merely, but of a massive ice- 

 cake, more universal than even in Southern Greenland now. Beneath this ice- 

 cake the soil, and all of life it supported, would be gradually harried away to the 

 sea, any traces of it left being nests of debris nitched into corners, ground over 

 and disturbed in every conceivable way by the ice above. Loose blocks w^ould be 

 carried off, porners would be rounded — the rock faces and the scrubbing-stones 

 would be striated — quantities of stones, gravel, sand, and mud would be ground 

 promiscuously together, and the tendency of the whole mass would be down- 



