PLIOCEITE PERIOD IN EKGLAKD. 513 



important in their bearing npon the events which I have been 

 tracing. In the excavation of the tnnnel at Mickleton, at the 

 northern extremity of the Cotteswolds, a bed of gravel was found 

 87 feet thick, which reposed on 15 feet of clay containing large 

 blocks of marlstone*. This bed of gravel was accumulated in a 

 strait which divided the small island formed by Ebrington Hill, 

 shown in Map 2 at the northern extremity of the large island 

 which the main Cotteswolds then constituted, and the elevation of 

 its top is 490 feet. It of course represents the entire gravel accu- 

 mulation from the time when during Stage II. Mickleton became 

 submerged, up nearly to the close of the Chalky Clay, a little before 

 which its top had emerged ; for from Mr. Gavey's description, it does 

 not appear that this gravel contained the red chalk and hard white 

 chalk of Lincolnshire, though Mr. Lucy mentions (p. 47 of his 

 paper t) that patches of gravel with white chalk and flints are 

 within the district where this bed occurs ; and in one pit of which 

 he gives a section, at Little Woolford fields, at an elevation of 

 394 feet, and in which 17 feet of this gravel is exposed, he found 

 both the red and the hard white chalk imbedded in it, as well 

 as the large angular flints so characteristic of the Chalky Clay. 

 This is on the north of the water-parting between the Thames and 

 Severn systems by way of the Evenlode and Stour, and in the 

 valley of the latter. IN'ear Chipping-Norton Eailway Junction, 

 however, which, though at a somewhat lower level than this last, 

 is on the south of this parting and within the valley of the Even- 

 lode J, he also found this debris ; and as it has not been noticed 

 within the Thames system further east, the inference is that 

 passing from the mouth of the Bain-Steeping trough, in Sheet 

 84, it was swept by field-ice through the vaUey of the Wel- 

 land and over the water-parting between this and the valley 

 of the Avon, and so into the sea over the Severn system. 

 Grinding along the coast of the islands shown in Sheet 53 of 

 Map 2, but which had then further emerged so that the channels 

 there shown as open between the systems of the Wen and Severn by 

 way of the Leam and of the Thames and Severn systems by way of 

 the Itchen and Cherwell had now closed, this ice was swept up the 

 valley of the Stour to the east of Ebrington Hill and of the now emerged 

 strait between that hill and the Cotteswolds, and so through one or 

 two narrow and shallow passages through the parting which were 

 still water-covered into the sea over the Thames system. The 

 closing of the parting between the Thames and Ouse systems in 

 Sheet 46, which I have described as having just preceded the end 

 of the Chalky Clay, is quite in accord with these inferences. 



The gravel which occurs abundantly within the drainage-system 

 of the Severn has yielded molluscan remains in many places, and 

 all of the same character ; but with the exception of the band of 

 fragments and worn shells which I have referred to the ploughing- 



* Gavey in Quart. Journ. Geol. Soc. vol. ix. p. 29. t Loc. cit. p. 475, ante. 

 \ The position of each of these occurrences is shown by the crosses in Sheet 

 44 of Map 2. 



