496 ME. P. W. HAEMER ON THE [NOV. 1907, 



The late Sir Joseph Prestwich, indeed, maintained that the 

 Thames (or Isis), originating in pre-Glacial times, ran towards the 

 "Wash, having been diverted to the south during the Glacial Period 

 by the excavation of the gorge at Goring. 1 



The map (PI. XXXIV) shows a line of low hills, occasionally, as 

 near Oxford, capped by gravel, which extend from Purton by 

 Faringdon and Wytham to Headington and Beckley, and thence to 

 Brill ; they seem to represent isolated portions of a former Oolitic 

 escarpment, principally Corallian. Such an escarpment, then perhaps 

 unbroken, might possibly have formed the southern slope of the 

 valley in which, the pre-Glacial river ran. 



The Oxfordshire Gravels. 



Some of the hill-gravels of Oxfordshire and Berkshire, attaining 

 in places a height exceeding 600 feet O.D., as at Nettlebed, were 

 correlated by Prestwich with the Westleton deposits of East Anglia, 2 

 and have been referred to under that name by subsequent writers, as 

 by Prof. J. W. Gregory, 3 Messrs. H. W. Monckton & R. S. Herries, 4 

 and Mr. H. J. Osborne White. 5 



There are other plateau-gravels, however, in the vicinity of 

 Oxford, near Goring Gap and elsewhere, reaching in places a height 

 of about 500 feet above sea-level, which have been regarded, 

 not only by Prestwich, but by most of those who have studied the 

 subject, as of Glacial age. Whether we consider their constituent 

 materials, or the conditions under which they may have originated, 

 it is difficult, I think, to come to any other conclusion. Mr. Osborne 

 White remarks that they differ both in distribution and in compo- 

 sition from those first named: the isolated hill-patches of the 

 former contrasting markedly with the wider spread of the latter. 6 



The gravels regarded as Glacial occur at various levels, but I 

 agree with Mr. White (op. cit. p. 11) in thinking that those of the 

 plateaux on the one hand, and of the lower terraces on the other, 

 are the extremes of one and the same series, the principal distinction 

 between them being the greater abundance in the former of rocks 

 foreign to the Thames basin. 



1 Quart. Journ. Geol. Soc. vol. xlvi (1890) p. 177. The Eev. A. Irving had 

 previously urged that the Kennet-Thames line of drainage represents the 

 original course of the Thames; the erosion of the Paugbourne (or Goring) 

 gorge, by which the Isis was diverted, taking place at a comparatively recent 

 period, Quart. Journ. Geol. Soc. vol. xliv (1888) p. 181. 



2 Rid. vol. xlvi (1890) p. 120. It seems desirable, however, to adopt some 

 other name for these deposits. The term now used implies their identity 

 with the pebbly gravels of Norfolk and Suffolk, as to which many people 

 are doubtful ; the identity, I think, rests upon very slender evidence. 



3 'Natural Science ' vol. v (1894) p. 98. 



4 Proc. Geol. Assoc, vol. xii (1891-92) p. 108. 

 6 Ibid. vol. xii (1892) p. 379. 



« Ibid. vol. xiv (1895-96) p. 27. 



