Ca. XVI1L] AKEA OF THE WEALDEN. 35^ 



ing erect on the spot where they originally grew, the sand having been 

 gently deposited upon and around them ; and similar appearances 

 have been remarked in other places in this formation.* In the same 

 division also of the Wealden, at Cuckfield, is a bed of gravel or con- 

 glomerate, consisting of water-worn pebbles of quartz and jasper, with 

 rolled bones of reptiles. These must have been drifted by a current, 

 probably in water of no great depth. 



From such facts we may infer that, Flg - 84T - 



notwithstanding the great thickness 

 of this division of the "Wealden, the 

 whole of it was a deposit in water of 

 a moderate depth, and often extremely 

 shallow. This idea may seem start- 

 ling at first, yet such would be the 

 natural consequence of a gradual and 

 continuous sinking of the ground in 



an estuary Or bay, into which a great Sphenopteris gracilis (Fitton), from the 



-,. -I i-i xi # j j. Hastings Sands near Tunbridge Wells. 



river discharged its turbid waters. a . A portion of the same magnified. 



By each foot of subsidence, the fun- 

 damental rock would be depressed one foot farther from the surface ; 

 but the bay would not be deepened, if newly deposited mud and sand 

 should raise the bottom one foot. On the contrary, such new strata of 

 sand and mud might be frequently laid dry at low water, or overgrown 

 for a season by a vegetation proper to marshes. 



Area of the Wealden. — In regard to the geographical extent of the 

 "Wealden, it cannot be accurately laid down; because so much of it is 

 concealed beneath the newer marine formations. It has been traced 

 about 200 English miles from west to east, from the coast of Dorset- 

 shire to near Boulogne, in France ; and nearly 200 miles from northwest 

 to southeast, from Surrey and- Hampshire to Beauvais, in France. If 

 the formation be continuous throughout this space, which is very 

 doubtful, it does not follow that the whole was contemporaneous ; be- 

 cause, in all likelihood, the physical geography of the region under- 

 went frequent changes throughout the whole period, and the estuary may 

 have altered its form, and even shifted its place. Dr. Dunker, of 

 Cassel, and H. von Meyer, in an excellent monograph on the Weal- 

 dens of Hanover and Westphalia, have shown that they correspond 

 so closely, not only in their fossils, but also in their mineral characters, 

 with the English series, that we can scarcely hesitate to refer the 

 whole to one great delta. Even then, the magnitude of the deposit 

 may not exceed that of many modern rivers. Thus, the delta of the 

 Quorra or Niger, in Africa, stretches into the interior for more than 

 170 miles,, and occupies, it is supposed, a space of more than 300 

 miles along the coast, thus formiug a surface of more than 25,000 



* Mantell, Geol. of S. E. of England, p. 244. 



f Fitton, Geol. of Hastings, p. 58, who cites Lander's Travels. 



