622 STKATIGRAPHICAL GEOLOGY 



The whole of Southern Scotland and Northern England below 

 the level of 1600 feet is more or less covered by boulder-clay, 

 which in many places has the same character as the Scottish till. 

 The larger boulders embedded in this till are striated in situ in the 

 same general direction and with the same firmness and evenness as 

 the striae on the underlying rocks ; thus the till of Northumberland 

 may be likened to one vast irregular " striated pavement." The 

 smaller boulders and stones frequently have their longer axes 

 drawn into the line of glaciation, as if by a heavy dragging force 

 moving contemporaneously with the arrangement of the material. 

 At the surface it is often shaped into sow-backs or drumlins 

 stretched in the same direction. All these features of the till are 

 remarkably developed on the watershed among the Bewcastle 

 Wastes, north of Gilsland in Cumberland. 3 



The composition of the till, again, shows that the outcrops of 

 rock lying in the path of movement all the way from the red 

 rocks of Cumberland, for instance, to the coaly shales of Newcastle 

 contributed one after the other their quota of material to the 

 mass of the clay. The texture and colour of the till thus constantly 

 varies it is bright Indian red on the red rocks ; leaden-coloured 

 and clayey on the carbonaceous rocks ; sandy where the pale 

 Carboniferous sandstones predominate ; brown on the Cheviot 

 porphyry ; and when it rests on composite formations such as the 

 Carboniferous limestone series, it never remains for half an acre 

 the same. Among the slopes of the higher hills it is thin, loose, 

 local, angular, and almost morainic-looking ; in the valleys and 

 low grounds it becomes dense and well-kneaded up, and contains 

 a larger assortment of boulders ; in the lower grounds it is often 

 gravelly and much intercalated with seams of sand, gravel, and 

 laminated clay ; but it is the same deposit throughout. 



In the south-west of Scotland, and especially in Ayrshire, 

 broken marine shells are found in the boulder-clay up to heights 

 of 1000 feet above the sea, and the precise manner of their con- 

 veyance against the outflow of the local ice has not yet been 

 explained. 



On the coast of Northumberland and Durham, however, there 

 is a newer or upper boulder-clay limited to the maritime districts, 

 and to elevations under 350 feet. It is divided from the till 

 sometimes by stratified sand and gravel, and sometimes by an 

 eroded junction line. It seems to be the same deposit, very 

 uniform in character, that is found along the sea -board from 

 Aberdeenshire southward, differing from the till by its uniformly 

 reddish colour and the fewness and smallness of its stones. 



