392 Proceedings of the Royal Physical Society. 



XXXIII. Note on a Recent Exposure of a " Washout " of 

 Strata in New Redhall Quarry. By James Bennie, of 

 the Geological Survey of Scotland. [Plate XVI.] 



(Read 16tli April 1890.) 



When miners in pit-workings find a seam of coal ending 

 abruptly in loose sand and gravel, and passing through the 

 same find the coal on the same level as before, they say the 

 coal has been " washed out " by a torrent of water, which has 

 left the sand and gravel in its place. The term " washout " 

 has been adopted by geologists when they find a hollow cut 

 out of the solid rocks, and filled in with boulder clay or the 

 rubbish of it, and the width and depth of the hollow is taken 

 as indicative of the volume of water and the time it took to 

 cut it out. I think this term admirably describes the appear- 

 ances in Eedhall Quarry, to which I wish to direct attention. 

 In the section presently exposed, the sandstone rock is seen 

 to rise in a humph — flanked on either end by a hollow 

 occupied by 10 or 12 feet of bituminous shale, and over all 

 extends a mass of boulder clay 20 feet or so in thickness. 

 The shale on both the east and west ends of the humph has 

 been truncated, and the boulder clay comes down as it were 

 and rests upon the sandstone rock at either end of the 

 section. At the east end nothing remarkable is seen, but at 

 the west end this extraordinary phenomena is displayed. 

 Upon the edges of the truncated shale rest first 3 feet of 

 boulder clay ; then that boulder clay itself is truncated, and 

 against the edges of both — that is, the boulder clay and the 

 shale beneath — abuts a confused mass of what can only be 

 regarded as rubbish from the boulder clay, consisting as it 

 does of rough grit and gravel, shivers of shale, oblong slabs 

 of sandstone, and rounded boulders of trap-rock and sand- 

 stone. It is evident that this mass of rubbish and boulders 

 has been washed out of the boulder clay, which doubtless 

 originally extended over the truncated edges of the shale on 

 the west end of the section, as it still does over the east end, 

 by some violent torrent of water, and redeposited in the 

 hollow. Over this confused mass of rubbish, 20 feet or so of 

 boulder clay has been deposited, overwhelming the whole. 



