264 AREA OF THE WEALDEIvJ. [Ch. XYIIl 



have been remai-ked in other places in this formation. "^ In the sam<^ 

 division also of the Wealden, at Cuck- 

 field, is a bed of gravel or conglomer- 

 ate, 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, 

 notwithstanding the great thickness of 

 this division of the Wealden, the whole Spiienopteru graciiiH~^~mxx). from th^ 

 of it was a deposit in water of a moder- ^^""^ ^'^'^^^ ^^^' Tunbridge Weiis. 



^ -i \ (> Tin ^- -A- portion of the same magnified. 



ate depth, and oiten extremely shallow. 



This idea may seem startling at first, yet such would be the Lutural con- 

 sequence of a gradual and continuous sinking of the ground in an estuary 

 or bay, into which a great river discharged its turbid waters. By each 

 foot of subsidence, the fundamental 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 con- 

 trary, 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 Dorsetshire 

 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; because, in 

 all hkelihood, the physical geography of the region underwent frequent 

 changes throughout the whole period, and the estuary may have altered 

 its form, and even shifted its place. Dr. Duuker, of Cassel, and H. 

 Yon Meyer, in an excellent monograph on the Wealdens of Hanover 

 and Westphalia, have shown that they correspond so closely, not only 

 in their fossils, but also in their mineral characters, v/ith 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 ot 

 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 forming a 

 surface of more than 25,000 square miles, or equal to about one half of 

 England.f 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 



* Mantel], Geol. of S. E. of England, p. 244. 



•j- Fittou, Geol, of Hastings, p. 58; -wbo cites Lander's Travels. 



