THE GLACIAL GEOLOGY OF NORTHUMBERLAND 99 



of formation of this bed is unknown, the evidence seems to 

 indicate that it marks the site of an early glacial stream which 

 flowed in a south-westerly direction, possibly towards the pre- 

 glacial Wansbeck. 



The other bed stretches northwards for half-a-mile from the 

 mouth of the Lyne Burn. It is from 6 to 15 feet thick, rests 

 on boulder clay, and is covered with drift sand. Its base is 

 about 10 feet above high water mark. At the south end the 

 gravel is clean and firmly cemented in places ; towards the 

 north the pebbles are less developed and embedded in dirty 

 sand. Sandstones and limestones (many reddish in colour) 

 are the chief constituents, and whinstone and magnesian lime- 

 stone are abundant. Of the far-travelled rocks the most 

 conspicuous are Cheviot porphyrites. Chalk and chalk flints 

 occur here, as at Horsebridge Head, along with greywacke, 

 mica schists, garnetiferous mica schist (Pitlochrie?), syenite, 

 quartz porphyries, trachyte and chert. 



From its position this bed might reasonably be regarded 

 as a raised beach. One may look upon it, on the other hand, 

 as a glacial gravel which has been laid bare by marine 

 erosion. If this view be provisionally accepted, then its 

 relationship to the Horsebridge Head deposit comes out in a 

 clearer light. Both are distinguished by containing chalk 

 flints, magnesian limestone, Cheviot porphyrites, and igneous 

 and metamorphic rock, probably of Scottish origin. One 

 occurs below typical boulder clay upon which rests a reddish 

 prismatic clay, the other lies on reddish prismatic clay under- 

 lain by typical boulder clay, and in both cases the typical clay 

 rests on the rock-surface in the immediate neighbourhood. 

 These facts point to a drift of ice from the north both before 

 and after the formation of the typical boulder clay, which has 

 a more westerly origin. The source of the later rocks 

 (Permian and Cretaceous) is unknown, but may possibly 

 be some outcrop in the North Sea. 



Summary of Evidence of Ice-Movement derived from 

 Striations a?id Transport of Glacial Material. — A cursory 

 inspection of the facts so far detailed will suffice to make clear 



