

CHAP. XIII.] PLEISTOCENE EPOCH. 263 



contain show that the ice under which they were formed 

 radiated outwards from the main watersheds of the country, 

 and they do not contain any intercalated marine deposits. 

 Elsewhere, as in Lewis, Caithness, Aberdeen, Arran, and 

 the central Lowlands, there are Boulder-clays which contain 

 broken sea-shells and include sands and gravels of marine 

 origin ; these deposits have not yet been found for certain 

 much above 500 feet, but Mr. Jamieson has described stra- 

 tified drifts occurring at a much greater height. Lastly, 

 there is a set of stratified deposits (soft sands, gravels, and 

 clays) which contain some Arctic species of shells, but do 

 not occur above the 100-feet contour line, and pass into 

 ancient river-gravels above that level. These last appear 

 to have been contemporaneous with the kames or eskers, 

 and with the moraines of the later glaciers in the Highland 

 valleys. 



This succession of deposits is particularly clear in Aber- 

 deenshire, where, resting on a rock-surface that is glaciated 

 from west to east, lies a tough grey Boulder-clay containing 

 stones which have clearly been brought from western loca- 

 lities, or derived from the rocks in the neighbourhood. 

 This clay varies greatly in thickness, as if it had suffered 

 from subsequent erosion, and is sometimes reduced to a 

 layer of grey rubbish and boulders. Above this, or in its 

 absence resting on a rock- surf ace that is glaciated from the 

 south and S.S.W., is a red Boulder-clay containing stones 

 which have come from localities to the southward. This 

 clay is sometimes as much as 100 feet thick, and it is asso- 

 ciated with sands and gravels which contain broken marine 

 shells ; it ascends to a level of 300 feet above the sea, and 

 gravelly deposits containing similar stones occur up to 500 

 feet. Lastly, by the estuaries of the Tay and the Earn, there 

 is a mass of stratified drift, the upper surface of which is 

 almost flat and is about 100 feet above the sea ; it main- 

 tains this level all the way from the coast to Dalreoch in 



