468- PEOCEEDrS-GS OF THE GEOLOGICAL SOCIETY. [Junc 3, 



I should premise first, by bearing testimoriy, so far as my own ob- 

 servations extend, to the careful and precise delineation of these 

 beds as distinguished from the [Middle Glacial Gravel, teimed by 

 him '• Gravel of the Lower Plain," which Mr. Hughes has made, so 

 that there can be no confusion as to the actual bed intended to be 

 discussed, since we found our resj)ective hues, where the districts 

 examined by us joined, to fit exactly; and secondly, by pointing out 

 that " this Gravel of the Lower Plain " is the same bed as that which, 

 in the form of gravel or of sand, I have traced as extending in a tor- 

 tuous track (due probably to its being a deposit of narrow channels) 

 beneath the great Boulder- clay (or Upper Glacial formation) through 

 Hertfordshire and Bedfordshire as far as Buckinghamshire and Lei- 

 cestershire on the north-west, and as emerging in a broader sheet 

 from beneath this Boulder- clay, over much of Essex, Suff'olk, and 

 IS^orfolk. Some years since, I pointed out that this sand passed over 

 the entire series of beds which form the Cromer-coast section, the 

 uppermost of which is the well-known contorted drift, and the 

 whole of which series (termed by me Lower Glacial) seems confined 

 to Xorfolk and the north of Suff'olk *. Since then I have been 

 engaged in regularly mapping the Glacial series over Suff'olk and 

 Norfolk in conjunction with ilr. Harmer of Xorwich, and we have 

 found abundant confirmation of this order of superposition being 

 correct : and I should observe that at the base of this lliddle Glacial 

 sand and gravel, and resting upon the upjDermost member of the 

 Lower Glacial series, namely, upon the contorted drift, there occui^s, a 

 few miles west of Lowestoft, a similar bed of Boulder-clay to that 

 described by Mr. Hughes as occurring at the base of the Lower- 

 Plain Gravel in Hertfordshire. I should further mention that from 

 gravel at Stevenage in Herls. in the midst of the brickearth-beds so 

 accurately described by Mr. Hughes as intercalated in this Middle 

 Glacial formation, I procured several specimens of Ostrea edulis, a 

 non-arctic shell which died out in the newer beds of the Crag, and 

 is unknown in the Lower Glacial series, and that Mr. Harmer and 

 myself have also obtained a Molluscan faima of twenty-six species 

 from this middle division ; but, as we hope hereafter to lay what we 

 regard as the structure and fauna of the Glacial beds of Xorfolk and 

 Suffolk before the Society, I need not here refer to them further. 



Is^ow the pebble-gravels (termed by Mr. Hughes " Gravels of the 

 Higher Plain ") occur on the highest London-clay summits, that 

 extend southward, from the termination of his section at Brickenden 

 Green, towards the Bagshot outliers of Hampstead and Harrow ; and, 

 although there remains no Glacial Clay over them, there can be little 

 doubt, I think, of these patches being a continuation of this " Gravel 

 of the Higher Plain." At Pinchley, however, some 100 feet or so 

 lower than the summit of the Bagshot outlier of Hampstead (on 

 which occur, as before mentioned, traces of the same pebble-beds 

 as those first described, and distinguished by the figiire 4 in the 

 accompanying section), we find this Gravel of the Higher Plain 



* See also the diagram-section at pp. .548 & 549 of tlae 22nd vol. of the 

 Society's Joiu'nal. 



