TIIK 1'I.KISTDCKNK SKIUKS 621 



than f>o feet thii-k and contain numerous broken marine shell-, 

 which seem to have been derived from the destruction of Pliocene 

 I'.eds, comparable to the English Crags. The red day varies IVoin 10 

 to 30 feet in thickness and reaches inland up to heights of 300 

 feet, while pebbly gravels with broken shells range up to 470 feet 

 In the basin of the Clyde there are certain deposits which were 

 evidently formed during the last stage of the Glacial epoch. The 

 usual succession of these beds is as follows : 



PI d ( "*' Sandy clay or sandy gravel. 



1,^1 -| 2. Fine grey clay with many perfect shells. 



\l. Laminated reddish clay without shells. 



Till. Hard tough boulder-clay with striated stones. 



There is always a layer of laminated, stoneless, and shell-less clay 

 1 iet ween the till and the shell-tearing clay (No. 2), but its thickness 

 varies from 1 to 18 feet. The clay above is a consolidated mud 

 through which many stones, both rounded and angular, are scattered, 

 but its consistency is not that of boulder-clay, and the stones are 

 not glaciated ; the shells which occur in it are generally perfect, 

 and are of northern and Arctic species. These clays fringe the 

 Finh of Clyde from Glasgow westward, and pass up the Kyles of 

 Bute to Loch Fyne ; they are also found on the shore of Loch 

 Lomond, but do not anywhere extend beyond 50 feet above the sea. 



Inland the last phase of the Glacial epoch is marked by the 

 occurrence of terminal moraines in many of the Highland valleys ; 

 sometimes several such moraines occur one above another, and 

 huge blocks of rock are often perched on the top of them as well 

 as on the neighbouring slopes, while the course of the glen above 

 the highest moraine is swept clear of all such detritus. 



2. Southern Scotland and North of England 



In this area there were three principal centres of dispersion, 

 one in Galloway, whence confluent glaciers moved outwards from 

 the central granitic hills, another in the Lake District already 

 mentioned (p. 617), and a third on the Hartfell, Bit-rick, and 

 Cheviot Hills, from which ice flowed chiefly eastward and south- 

 ward (see Fig. 202). In each area the northward flow was short, 

 and the main lines of transport were south and south-east. Thus 

 Kskdale granite is found all over Lancashire and Cheshire, and 

 boulders from the fells near Shap have been carried not only down 

 the valley of the Lune, but over the Ingleborough district into 

 Ribblesdale, showing that at one time the ice over-rode hills up to 

 1500 feet above present sea-level. Another stream of boulders has 

 passed through the Stainmoor pass and through Teesdale to the 

 east coast of Northumberland. 2 



