LAMPLUr.TI : L.WD-SHKLLS I\ INFRA-fa.ACIAL rHALK-RUBBLE. 93 
prevailed ininiediately before tlie invasion of the district b}^ 
the ice-sheet. 
Besides chalk fragments, however, the bed contains a fail' 
sprinkling of small chips of gre\^ Hint and of well-rounded grains 
of quartz-sand. Close search also reveals the presence of a few 
small fragments of hard grey grit or quaitzite and of other 
stones foreign to the district, including a greenish basaltic 
rock, though these are very rare. The occurrence of the 
flint chips is remarkable, as the chalk which forms the neigh- 
bouring slopes contains no flint, and the nearest outcrop of the 
flinty Middle Chalk, from which the fragments appear to have 
been derived, lies over two miles distant to the northward, 
and is separated from these slopes by the wide j^re-C^lacial 
depression of the Bempton Valley. 
Another significant fact is that although the bed at this 
place is made up almost exclusively of fine detritus, I noticed 
in the cliff-section during a previous visit to the locality (in 
November, 1902) an angular block of hard yellowish-white 
sandstone or grit, measuring 1| feet by \h feet by 1 foot, 
embedded at the base of the rubble just above the blown sand 
of the Buried-Cliff Beds. This boulder is piobably from the same 
source as the small fragments of grit mentioned above. It is 
the only large boulder which I have seen in the chalk-rubble 
at Sewerby, though many years ago I found a boulder of 
quartzite 21 inches in diameter in the chalk-wash which under- 
lies the drift at Danes' Dyke, 1| miles farther eastward.* It is 
noteworthy that a few erratic stones, chiefly of sandstone and 
basalt, w^ere obtained in excavating the old beach-deposit at the 
foot of the Sewerby buried cliff ; and that in the land- wash 
which rested on this old beach and was covered by blown sand, 
we found four species of small land-shells, including the species 
which has now been found in the chalk-rubble. t 
* " Drifts of Flamborough Head," Quart. Journ. Geol. Soc, vol. 
xlvii., p. 397. 
t Reports on the Bviried Cliff, op. cit. 
