96 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Juiie 13> 



island, which region, although at 2000 feet lower level than at pre- 

 sent*, would still have presented a wide area, and ranges of some 

 thousand feet of elevation. It is diminished area and elevation which 

 at present unfit the West of England to produce that growth of oak 

 and gigantic fir which before the period of the drift seems to have 

 clothed every portion of the region of Dartmoor, and which would 

 still more be unfitted for it when at its lower pleistocene level : on 

 such low districts, however, and in a chmate modified by a sur- 

 rounding sea, some portion of a previous flora might have been 

 enabled to live on. 



An examination of those portions of the several formations which 

 occur within short distances of the coast-line of the Channel valley 

 on eithey side, tends strongly to establish the supposition of a re- 

 currence of like conditions along the same area at several distinct 

 geological epochs. 



The thick beds of shingle at certain places in South Devon (Ugbrook, 

 Connator, &c.) indicate the proximity of the littoral zone of the car- 

 boniferous deposits ; these beds occur upon a group of strata, which 

 agaiQ indicate a series of antecedent local elevations, attended with the 

 diffusion of trappean matter, over which zoophytes constructed the 

 Devonian coral reefs : on the other side of the Channel the limestone 

 masses of the Cotentin were evidently formed under like conditions, 

 and at the same time : lower than these in the same series occurs the 

 coarse shingle of the French and Jersey slate rocks. 



At the subsequent period of the new red sandstone, the lower 

 beds constantly suggest conditions of marginal accumulation : the 

 movement which attended the accumulation was one of gradual sub- 

 sidence, but the sheet of porphyritic matter which contributed so 

 much material to the new red conglomerate must have been for a con- 

 siderable period at the water-level, as high in the series, and after an 

 enormous amount of accumulation, large blocks of porphyry have 

 been thrown down over beds which from their composition must have 

 been deeper-water deposits than such as occur beneath them. The 

 condition of the materials along the edge of the new red sandstone 

 group in Calvados and La Manche is often that of true shingle, of 

 great thickness, composed of the quartzose rocks of the district. The 

 older strata of this part of France run east and west, and this ele- 

 vation was acquired before the new red sandstone period ; so that 

 we seem to have the direction of an area of dry land east and west, 

 and that of a line of coast shingle conforming to it. From this coast- 

 line the new red sandstone sea stretched away north and east with 

 an increasing depth, except where, as in South Devon and Somerset, 

 islands presenting coast-masses of limestone or porphyry rose to the 

 surface, from the spoil of which the coarse conglomerates were formed. 

 The great blocks of porphyry of the middle beds of the new red 

 series in the West of England, included in sands and marls, indica- 



* Nicol " On Recent Formations near Edinburgh," Quart. Journ. Geol. Soc. 

 vol. V- p. 23. 



