388 Glacial Epoch. 



consist of Coal-measure sandstones and conglomerate, 

 Carboniferous Limestone, and more sparingly, Lammer- 

 muir grits and granite. In pits thirty feet in depth, 

 beneath sands, the clay is very fine, containing a few 

 scratched stones, and we were informed that this clay 

 has been sunk through to a depth of fifty fathoms 

 (300 feet), so that the bottom of this pre-glacial river- 

 valley is much below the level of the sea. 



Under Tynemouth, at the mouth of the river, there 

 is a high cliff of stiff Boulder-clay, about 50 or 60 feet 

 in height, facing North Shields. Stones and boulders 

 large and small are scattered all through the clay from 

 bottom to top approximately in the following propor- 

 tions : 



Carboniferous Sandstone i. . 34 

 Limestone . . 27 



Coal . . 10 80 per cent, 



Ironstone ... 5 



Shale . . .4. 



Lamm ermuir grit . . - . . .19 

 Greenstone . . . . -, . 1 



There are several irregular thin bands of gravel 

 and sand in the Till. It will be observed that except- 

 ing two insignificant outlying patches of Magnesian 

 Limestone at Tynemouth, all the rocks up to and beyond 

 the borders of Scotland belong to the Carboniferous 

 series, and the result is, that of the ice-borne erratics , 

 80 per cent, belong to these formations, and only 19 

 per cent, to the more distant Silurian grits of the 

 Lammernmir range. 



At Sunderland, about a mile north of the harbour 

 light, there is a section of boulder-clay lying on the 

 Magnesian Limestone. The surface of this rock has 

 been polished by glacier ice, and the striations trend 

 very nearly from north-east to south-west. The over- 



