IN THE ISLE OF PORTLAND AND AROUND WEYMOUTH. 51 



in the neighbourhood of Weymouth, the evidence is not very clear. 

 Judging from the levels of these beds, they may probably be 

 referred to different periods, extending from one shortly subsequent 

 to the elevation of the anticlinal axis, to the one when the streams 

 had obtained their present position and present level. Thus the 

 small patch capping the hill beyond Preston may be the oldest (&") ; 

 the patch between Chickerel and Portisham, and those on the hills 

 near Osmington Mills, and which consist chiefly of large chalk-flints, 

 may be the next (&') ; those above Badipole and the Portland Ferry, 

 third ; while that in which the remains of the mammoth have been 

 found is confined to the low-level beds of Eadipole and is the last (a). 



But the most anomalous mass is that between "Weymouth and 

 Chickerel. It is composed, as before observed, almost entirely of 

 subangular fragments of Greensand chert. The lie of the land, 

 which intercepts communication with the Abbotsbury hills, and the 

 presence of the more composite drift both to the north and south, 

 lead me to suppose that this Greensand drift may have been derived 

 rather from the district of the White Nore before the excavation 

 of Weymouth Bay than from that of Abbotsbury ; but I must leave 

 this question open. It does not seem connected with any river-gravel. 

 The drift between Wyke and the Perry, where we get Greensand 

 chert, chalk-flints, and Portland ohertmixed, may possibly be assigned 

 to the same age. 



On the other hand, regarding the drift in the Upway valley and 

 at Eadipole as a low-level valley gravel, that on the hill east of 

 Eadipole, which contains an abundance of Tertiary debris together 

 with chalk-flints brought down from the hills at the head of the 

 Upway valley, may be a high-level gravel of the same river-system. 



Such, briefly, appear to be the very remarkable series of pheno- 

 mena which, at a comparatively recent geological time, have given 

 form and shape to the district round Weymouth. Carrying our view 

 back to the latter part of the Glacial Period, before the present 

 valley-systems or even some of our plains were elaborated, a broad 

 tract of Chalk, bounded in places by Greensand, and capped by Ter- 

 tiary beds and older gravels, rose inland ; and with these the Purbeek 

 and Portland beds were brought into level juxtaposition by and along 

 the great line of fault running westward and eastward nearly midway 

 between Dorchester and Weymouth. From that district the surface 

 of the country sloped gradually to the south end of Portland ; and over 

 this surface, which then bridged over the plain of Weymouth, streams, 

 originating in the Chalk, Greensand, and Tertiary district, flowed 

 southward to the Channel. It was one of these streams which, 

 passing over Portland, rolled down to that island pebbles derived 

 from those several newer formations, while the floods and ice of 

 winter carried down the larger Sarsen-stone boulders also so common 

 in the same fluviatile bed, and entombed the remains of the elephant, 

 horse, &c, then living in that area. 



At this time the line of coast extended, much as it does now, but 

 with fewer and deeper bays, from the shores of Cornwall, passing close 

 to Plymouth, touching the headlands of Berry Head, Start Point, and 



e2 



