O.N THK ERRATIC BLOCKS OF THE BRITISH ISLES. 243 



south of Stoup Beck. The long axis is directed about N. 30° W., and 

 the southern end is slightly raised, in which respect it resembles the great 

 majority of the large boulders in the same deposit. 



The base of the boulder is about 4 feet below an ill-defined junction, 

 between a dark bluish-brown boulder clay, very heavily charged with 

 stones and traversed by shear planes, often much contorted, and an upper 

 paler dun clay with fewer stones. It iiiay be that the differences of 

 aspect are due to differences in exposure to spray. 



The lower clay was examined carefully to discover with what group- 

 ing of erratics the Shap granite boulders were associated, and every stone 

 of obviously foreign derivation was scrutinised especially with the object 

 of ascertaining whether the porphyrites of the Cheviot type and Grey- 

 wacke sandstones, such as occur in the Tweed Valley above Melrose, 

 were present in such numbers as to identify the boulder clay with the 

 beds forming the highest members of the Glacial Series in many parts of 

 the coast tract of Yorkshire. 



Porphyrites formed the predominant element of the foreign stones, 

 but they were mainly of a veiy dark-purple tint ; while the red por- 

 phyrites that preponderate in the Cheviots were represented by few- 

 examples. The Greywacke sandstone, including a perfectly angular 

 slab 2 feet in length, did not resemble any type that I have seen in the 

 Tweed Valley. 



Decomposed melaphyres with amygdaloids were common ; basalts and 

 dolerites less so. Two pebbles of trachyte were found and one pebble of 

 rhomb porphyry. Three flints (not of Yorkshire type), one small pebble 

 of granite, a granophyre (possibly Buttermere), one piece each of Brockram 

 and Old Red sandstone, some Carboniferous limestone, and Magnesian 

 limestone completed the series of certainly foreign stones. 



Of local, or possibly local, rocks the following were observed : — 



Sandstones from the Estuarine Series (these constituted nearly the 

 whole of the large blocks and many of the smaller stones). 



Equisetum stem. 



Harpoceras bifrons. 



Jet (abundant). 



Middle Lias ironstone. 



Lower Lias shale and limestone. 



Gryphcea inourva. 

 . Oxynoticeras oxynotum. 



Gypsum (a lump as large as a cricket-ball). 



Reported by Mr. Thomas Sheppard, F.G.S. 



Front, Withernsea. — A boulder of black flint containing a specimen of 

 Belemnites lanceolatus. 



Black flints of this type have long been known in the glacial beds 

 of the Yorkshire coast, and B. lanceolatus has been collected in large 

 numbers ; but this observation shows them to have a common origin. 



As neither the black flints nor B. lanceolatus is known in the British 

 chalk, it is concluded that these have probably been derived from an 

 outcrop beneath or beyond the North Sea. 



From Dimlington.— A. rounded boulder of quartz- rhomb-porphyry,' 

 a rock only once previously recorded, viz. from Burstwick. 



'. See Harker, Proc. Yorks Geol. Soc, vol. xiii. pt. ii. pp, 279( 281. 



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