210 DE. R. L. SHEELOCK AXD ilE. A. H. ^^OBLE ON THE [JuilG 1 912, 



case the river had been diverted southwards, leaving the awkward 

 bends at Crawlej^ and Bourne End at the point of diversion. This 

 fact suggested capture by a small stream to the south of the old 

 river-course, cutting back its head-waters. In each case the 

 abandoned course was over clays, whereas the new one was in 

 limestone ; the cutting back of the head-waters of the capturing 

 stream might, therefore, be accomplished by solution along joint- 

 planes. 



Mr. A. L. Leach remarked that, on the Xorth Downs in the 

 vicinity of the Darent and the Medway, the superficial deposits, 

 which appeared to resemble those described by the Authors, 

 included Clay-with-Flints and brick-earths associated with scattered 

 sarsens and drift -gravels. The resemblance between the two sets 

 of deposits certainly suggests similarity of origin ; but the Clay- 

 with-Flints of the Xorth Downs cannot be ascribed to any ice-sheet 

 advancing from the north-west. He had been desirous of learning 

 what were the special characters which the Authors regarded as 

 criteria of the Glacial origin of the Clay-with-Flints in the area 

 described, and this part of the subject had not been fully brought 

 out. It certainly appeared significant that no ice-scraped flints had 

 been found ; yet, if ice had actually passed over this mass of clay 

 and flints with which hard siliceous sandstones (sarsens) were 

 abundantly associated, the conditions would not have been 

 unfavourable to the production of striations. 



The Eev. E. C. Spicee commented upon the Walter's Ash deposits, 

 and pointed out that the clay containing the large sarsen-blocks 

 contained no flints, but rested in Chalk hollows 50 or 60 feet deep, 

 lined by a thickness of a few feet of Clay-with-Flints. These 

 crater-like pits, filled with laminated clays, were also covered over 

 by a thin 'drift' deposit of mixed materials ; but, since the plateau 

 containing these pits was here 6-10 feet high, it was difiicult to 

 imagine a mass of ice of that thickness advancing over the Chilterns 

 without blocking the Goring Gap, and thus preventing the Thames 

 from flowing to Bourne End. There was undoubted Boulder Clay 

 near Wolverton. He considered that the Brick Hills standing in 

 front of the Chiltern escarpment, but lower, should show strong 

 evidence of Glacial deposits, which the speaker had not found upon 

 the sandy surface. If the theory of the paper were accepted, it 

 would be necessary to reconsider the topography of the whole 

 Oxford region. The maj^ping of the observed deposits, however, 

 was a very valuable contribution. 



Dr. A. E. Salter stated that he could not agree with the last 

 speaker concerning the evidence of 'Glacial' deposits in front of the 

 Chiltern escarpment. Drift and boulders occurred on the highest 

 points of the Lower Greensand area (above 500 feet O.D.), near the 

 Brick Hills. At Great Brickhill, near the AYesleyan Chapel, is a 

 section in chalky drift, about 20 feet deep, and Boulder Clay can 

 also be seen in a pit on the right-hand side of the road leading from 

 Heath to the ' Fox & Hounds ' and Sheeps Lane, at a height of 

 420 feet above O.D. 



