the Purbeck and Wealden Deposits of England and France. 275 



channel north-westwards between Scotland and Ireland ; another 

 in Northamptonshire and the counties immediately south-east 

 of it, forming the north-eastern opening; a third to the south- 

 east in the department of the Cote d'Or, communicating with 

 the Jurassic sea of the Jura and Alps ; and the fourth in the 

 south-west, forming a strait communicating with the Jurassic 

 basin of the Charentes and Pyrenees. Of these openings, that to 

 the south-east is considered by M. Elie de Beaumont to have 

 closed after the termination of the Stonesfield oolite*; that to 

 the north-west, Mr. Hullf, from a consideration of the manner 

 in which the sediment of the Jurassic deposits of the central 

 counties of England that are older than the upper zone of the great 

 oolite has been accumulated, regards as having closed about the 

 same epoch. The opening to the south-west would appear, from 

 the grouping of the Jurassic beds of the region, to have closed 

 also during the age of the great oolite ; but the position of the 

 basin of the Charentes and Pyrenees, the presence in the Cha- 

 rentes of the Portland limestone, and of a formation identical 

 with the English Purbecks, coupled with the absence there of 

 the older cretaceous deposits, induce me to suppose that a strait 

 continued open, joining the Anglo-Frankish basin to that of the 

 Charentes, until the close of the Purbeck epoch. The absence of 

 the lower cretaceous deposits in the Charentes basin, when taken 

 in connexion with the effects produced there by the upheaval of 

 the Pyrenees, points to the conclusion that the only access of this 

 depression to the sea was through a strait communicating with 

 the Anglo-Frankish basin, which, when elevated, converted that 

 of the Charente into land, or into a freshwater lake, until the up- 

 heaval of the Pyrenees, breaking up the barrier Atlantic-wards, 

 gave the sea entrance to that basin from the west. That infer- 

 ence will derive much support if it should prove, as contended 

 by M. Coquand, that lower cretaceous formations do not exist, as 

 hitherto supposed, in the Pyrenees, and consequently not in any 

 part of the Charento-Pyrenean depression. 



By the close of the Portland oolite and sand formation, the 

 only opening remaining unclosed, except the Charente Strait, 

 was that to the north-east; and if the assumption that the 

 Charente basin opened only into the Anglo-Frankish one be 



* The presence of cretaceous beds in the departments of the Doubs and 

 Jura conformable to the Jurassic, mentioned by M. Benoit and others, does 

 not prove that the upheaval of the Cote d'Or system of M. de Beaumont 

 took place at a later period than that assigned to it by M. de Beaumont, 

 but only that the upheaval of the system was of less extent than he consi- 

 dered it, and was distinct from the subsequent upheaval of the Jura and 

 part of the Cote d'Or during the cretaceous epoch, an upheaval possessing 

 a direction more east and west than the former, and crossing it at acute 

 angles. See Benoit, BulL vol. xv. p. 316. 



t See the paper last referred to. 



T2 



