﻿Mr. S. V. Wood on the Denudation of the Valley of the Weald, 319 



those of Tallowbridge and Kiltorkan in Ireland, the greywacke of 

 the Vosges and the sonthern Black Forest, and the VerneuiUi-shaies 

 of Aix and St. John's, New Brunswick. These concordant floras he 

 considered to mark a peculiar set of beds, which he proposed to 

 denominate the " Ursa-stage." The author remarked that the flora 

 of Bear Island has nothing to do with any Devonian flora, and that 

 consequently it and the other floras, which he regards as contempo- 

 raneous, must be referred to the Lower Carboniferous. Hence he 

 argued that the line of separation between the Carboniferous and 

 Devonian formations must be drawn below the yellow sandstones. 

 The presence of fishes of Old-Red- Sandstone type in the overlying 

 slates he regarded as furnishing no argument to invalidate this con- 

 clusion. The sandstones of Parry Island and Melville Island are 

 also regarded by the author as belonging to the " Ursa-stage," 

 which, by these additions, presents us with a flora of seventy-seven 

 species of plants. The author remarked upon the singularity of 

 plants of the same species having lived in regions so widely separated 

 as to give them a range of 26^° of latitude, and indicated the rela- 

 tions of such a luxuriant and abundant vegetation in high northern 

 latitudes to necessary changes in climate and in the distribution of 

 land and water. 



2. " On the Evidence afforded by the Detrital beds without and 

 within the North-eastern part of the Yalley of the "Weald as to the 

 mode and date of the Denudation of that Yalley." By S. Y. "Wood, 

 Jim., Esq., F.G.S. 



The author commenced by discussing the various hypotheses that 

 have been proposed to explain the denudation of the Weald Yalley. 

 In his opinion the upheaval of the district took place in Postglacial 

 times, and subsequently to the deposition of the gravels of the 

 Thames Yalley, of East Essex, and of the Canterbury heights ; and 

 the denudation was effected chiefly by tidal erosion during gra- 

 dual upheaval in an inlet of the sea, aided by the action of fresh 

 water flowing into this inlet from the north by streams draining 

 the land which now constitutes the counties of Middlesex and 

 Essex. The chief evidence in favour of his views is as follows : — 

 1. The absence from the glacial beds of Essex of any debris repre- 

 senting a considerable denudation of the Weald during the glacial 

 period, and the probability that the Wealden area was beneath the 

 sea during the deposition of the Boulder Clay. 2. The comparative 

 absence of Lower Cretaceous or Hastings-sand materials from the 

 Postglacial gravel- sheets outside the north of the Weald. 3. The 

 impossibility of reconciling the presence of Tertiary pebbles in cer- 

 tain Weald-gravels with an origin by means of streams flowing in 

 the direction of the present rivers. 4. The antagonism between the 

 character of the major valley of the Weald and that of any excava- 

 tion producible by the agency of rivers. 5. The persistence of the 

 old coast contour with the river-drainage entering it from the north. 

 6. The existence of a cause, in the shape of an isthmus at Dover, 

 sufficient to induce a strong tidal scour. 



