352 LOWER CEETACEOUS AND WEALDEN FLORA. [Ch. XVIII. 



square miles, or equal to about oue half of England.* Besides, we 

 know not, in such cases, how far the fluviatile sediment and- organic 

 remains of the river and the land may be carried out from the coast, 

 and spread over the bed of the sea. I have shown, when treating of 

 the Mississippi, that a more ancient delta, including species of shells, 

 such as now inhabit Louisiana, has been upraised, and made to 

 occupy a wide geographical area, while a newer delta is forming ; * 

 and the possibility of such movements, and their effects,, must not be 

 lost sight of when we speculate on the origin of the Wealden. 



If it be ashed where the continent was placed from the ruins of 

 which the Wealden strata was derived, and by the drainage of which 

 a great river was fed, we are half tempted to speculate on the former 

 existence of the Atlantis of Plato. The story of the submergence 

 of an ancient continent, however fabulous in history, must have been 

 true again and again as a geological event. 



The real difficulty consists in the persistence of a large hydrographi- 

 cal basin, from whence a great body of fresh water was poured into the 

 sea, precisely at a period when the neighboring area of the Wealden 

 was gradually going downward 1000 feet or more perpendicularly. 

 If the adjoining land participated in the movement, how could it es- 

 cape being submerged, or how could it retain its size and altitude so 

 as to continue to be the source of such an inexhaustible supply of 

 fresh water and sediment? In answer to this question, we are fairly 

 entitled to suggest that the neighboring land may have been station- 

 ary, or may even have undergone a contemporaneous slow upheaval. 

 There may have been an ascending movement in one region, and a 

 descending one in a contiguous parallel zone of country ; just as the 

 northern part of Scandinavia is now rising, while the middle portion 

 (that south of Stockholm) is unmoved, and the southern extremity in 

 Scania is sinking, or at least has sunk within the historical period, j 

 We must, nevertheless, conclude, if we adopt the above hypothesis, 

 that the depression of the land became general throughout a large part 

 of Europe at the close of the Wealden period, and this subsidence 

 brought in the cretaceous ocean. • 



The flora of the Wealden and the Lower Greensand is characterized 

 by a great abundance of Conifers, Cycadese, and Ferns, and by the 

 absence of leaves and fruits of dicotyledonous angiosperms. The dis- 

 covery, in 1855, in the Hastings beds of the Isle of Wight, of 

 Gyrogonites, or spore-vessels of the Chara, supplied a link between 

 the secondary and tertiary flora which was previously wanting. 



* See above, p. 84 ; and Second Visit to the U. S., vol. ii. chap, xxxiv. 

 f See the Author's Anniversary Address, Geol. Soc, 1850, Quart. Geol. Journ. 

 vol. vi. p. 52. 



