Ixvi PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



the same areas. "We are not to suppose that all the rivers of the world 

 suddenly ceased to transport detritus into lakes and seas ; that the 

 breakers no longer wore away the coasts, or that animal and vegetable 

 life was entirely destroyed, because we find a break in the sequence 

 of accumulations in a particular portion of the earth's surface. We 

 have now learned, by the progress of our science, to account for such 

 local breaks, and among other things, that dry land cannot fail to 

 show them, when such dry land, after submergence, is covered by 

 marine deposits, and is again upraised above the water. Hence all 

 evidence as to the passage of supracretaceous into cretaceous deposits, 

 such as that noticed by Sir Roderick Murchison in this paper, is im- 

 portant ; and the Society has reason to be satisfied that our colleague 

 has selected it as the channel through which to convey his extended 

 researches on the region noticed to the public. 



Movements which Mineral Masses may have sustained subsequently 



to their Accumulation. 



Mr. Weston, availing himself of the means afforded by a railway 

 cutting (upon the AVilts, Somerset and Weymouth line), points out 

 the facts he considers to be shown where the railway crosses the great 

 Ridgway fault, one formerly described in your Transactions by Dr. 

 Buckland and myself from appearances exhibited on the ground by 

 ordinary sections. It will be in your recollection that the great 

 movement which throws off the rocks on the north and south, thus 

 thrusting up the Wealden country of Kent and Sussex, and which 

 extends westward so as to form a marked anticlinal line to the 

 frontier of the green sand and chalk escarpments on the south of 

 Frome in Somersetshire, is accompanied by a more southern and par- 

 allel line of movement, crossing the Isle of Wight and extending into 

 Dorsetshire. It seems clear from the rocks disturbed, that this move- 

 ment took place after the Headon Hill tertiary deposits of the Isle of 

 Wight, since they have been included in it. Faults having a general 

 east and west character are seen on this line of movement, but as 

 faults having the same general direction are sufficiently common in 

 districts merging into this, and where flexures of the kind previ- 

 ously noticed are not to be found, it is not so clear that faults such 

 as those of the Ridgway are really contemporaneous with the arching 

 and bending of the beds by the side of, and through which they run. 



It will also be in your recollection, that after the dry land of the 

 Wealden time became depressed beneath the level of the sea, the 

 marine deposits of the cretaceous scries covered them over, and in 

 such a manner that the chalk and uppqr green sand extended over the 

 first-formed and lower part of the series, overlapping various older 

 beds in succession, even reaching as far as the coal-measures of Devon- 

 shire on the westward, and over the oolitic districts of Yorkshire on 

 the north. Probably also this overlap was far more extensive, though 

 denuding influences have so acted during the lapse of geological time, 

 that no certain marks remain to prove the amount of area covered by 

 the cretaceous series in Great Britain. W!e are certain at all events 



