284 Reports and Proceedings — 



tlie edges of which have been bent by a force assailing the hill from 

 the N.W. ; and as these edges have been shattered so as to form 

 parcels of slate-chips covered by, or rolled up in laminated sand, 

 along with parcels of clay, be endeavoured to prove that a stranding 

 of the floating-ice which must have brought part of the erratics 

 (including numerous chalk-flints), will alone account for the pheno- 

 mena. After describing patches of gravel and sand in other parts 

 of Caernarvonshire, referring to the Three-Eock Mountain deposits 

 in Ireland (which must have come from the N.W.), and briefly 

 noticing the drifts on Halkin Mountain, Flintshire, he entered upon 

 the main subject of his paper, namely, the discovery of an extensive 

 series of marine drifts, including (besides deposits on flat ground) 

 about twelve hillocks or knolls, consisting of rounded gravel and 

 sand, and in at least two instances, containing gravel-pits with 

 numerous shell -fragments. They extend along the east side of ' the 

 northern part of the mountain-range which runs between Minera 

 and Llangollen Vale, and are situated at levels between 1100 and 

 1300 feet above the sea. The gravel is largely made up of rounded 

 Eskdale-granite pebbles, and during his last or fourth visit to the 

 district, he found a large granite boulder on the axial summit of the 

 ridge, about 1450 feet above the sea, showing a submergence of the 

 mountain to at least that extent. He went on to assign reasons for 

 believing that the sea lingered longer at the level of the sand and 

 gravel knolls than lower down and higher up, so as to allow time 

 for the extra rounding of the pebbles, accumulation of erratics, and 

 multiplication of Mollusca ; for he could discover no reason for 

 supposing that the mollusks which left the shells did not live on or 

 near the spot in the littoral or sublittoral zone. He then described 

 a small exposure of high-level rounded gravel and sand near Llan- 

 gollen, and dwelt on the remarkable fact that the marine deposits 

 on Moel Tryfan, Three-Rock Mountain (Ireland), Minera Mountain, 

 and in Macclesfield Forest, occur at about the same altitude above 

 the sea-level. After proposing a provisional classification of the 

 drift-deposits of North Wales and the Pennine hills into zones, 

 showing probable variations in the rate of submergence, he concluded 

 by discussing the question, Whether the submergence was caused by 

 the subsidence of the land or the rising of the sea, without venturing 

 to express any decided opinion on the subject, but inclining to the 

 former idea. 



2. " On the Correlation of the Upper Jurassic Eocks of England 

 with those of the Continent." By the Eev. J. F. Blake, M.A., 

 F.G.S. Part I. The Paris Basin. 



This was an attempt to settle the many questions of correlation 

 arising out of the detailed descriptions given of the various localities 

 in the Paris basin where Upper Jurassic rocks are developed, by a 

 consecutive survey of them all ; undertaken by the aid of a grant 

 from the " Government Fund for Scientific Eesearch." In previous 

 papers the names used for the great subdivisions and their boun- 

 daries were adopted without material modification ; in the present 

 such modifications were proposed as may bring the English and 

 continental arrangements into harmony. 



