Bo ulder- Clay. 389 



lying clay has the character^ of genuine Till, and the 

 change in the direction of the striations from those pre- 

 viously noticed, may possibly be due to the pressure of 

 the inferred Scandinavian ice-sheet, which is supposed to 

 have united with that coming from Scotland, and may 

 for a space have deflected the line of its onward march 

 from the NNW. On the other hand, it may be a mere 

 local accident connected with a later part of the Glacial 

 epoch, when a distinct individual glacier flowed from the 

 far western watershed, more than a thousand feet in 

 height, about the sources of the Wear, which may have 

 spread into a fan-shape as it reached what is now the 

 shore. Such smaller glaciers existed, for in these 

 long dales of Durham and Yorkshire there are distinct 

 moraines, which mark the gradual decline of the glaciers, 

 and through which, and through the Boulder-clay, the 

 rivers have cut their modern channels. 



Stones derived from the Magnesian Limestone first 

 appear in the Till south of Tynemouth. In the neigh- 

 bourhood of Sunderland, the percentage of various kinds 

 of rocks seems to be nearly as follows 



Carboniferous Sandstone . . . 29 > 

 Limestone . . .21 



Coal 6 59 per cent. 



Shale . . . . 2 ' 



Magnesian Limestone 22 



Lammermuir grits, &c. . . . . . 16 



Greenstones and Basalts . . . 4 ,, 



The cliff is about 30 feet in height, and shows the 

 section given in fig. 82. 



The Till seems to have been worn on the surface 

 before the deposition of 3 and 4. 



It will be observed by consulting any geological 

 map, that, as in the previous case, the large percentages 



