A. Tylor — Formation of Deltas. 397 



"below would transmit pressures unequally along the axial line and 

 at right angles to it, on account of varying rigidity, and would ac- 

 count for unequal elevation to some extent along the axial line of 

 greatest elevation. 



The tides would rise much higher at the extremity of both the 

 English Channel and German Ocean before the perforation of the 

 Straits of Dover than they do now, and a rise of tide in the Thames 

 and Somme equal to that in the river Wye would explain many 

 difficulties. 



When the breach off Dover was made sufficiently wide to unite 

 the two seas, the tide would not rise to its former height, and this 

 would give the appearance of the sea-beaches along the coast having 

 been raised, and not that of the sea-level being lowered. 



The shingle flats near Calais and at Dungeness are analogous in 

 character and level. 



The Antwerp Crag and the true Norwich or Mammaliferous Crag are 

 also at a very low level and near the present estuaries. 



The shells in a well-section at Permerunde, North Holland, ob- 

 served by Mr. Burnell in 1852, were marine, but there was evidence 

 of an old land-surface at 56 feet below high-water mark, and this 

 seems to match the level of the submarine forests all round the 

 British coasts, and the sections in Cornwall in which Colenso found 

 tin-stone gravel, mammalian and human remains, below the later 

 marine or estuary deposits (page 407, De la Beche, Devon and 

 Cornwall). 



At Pentuan, Cornwall, human remains, skulls, are stated to have 

 been found under 40 feet of detrital accumulations, also mingled 

 with the remains of deer, oxen, hogs, and whales (page 404, op. cit.). 

 Mr. Colenso describes a piece of shaped wood, on the upper part of 

 the silt, that reposes upon the remains of a submarine forest, the 

 trees of which have grown upon the tin ground. Eemains of man 

 mingled with those of deer and other animals were found at Carnon, 

 among wood, leaves, and nuts, 53 feet below the river- wash (see also 

 Geological Transactions, vol. iv., 1817, p. 404). 



Section at Carnon Stream Tin Works : — 



1. Mud and sand, 7 feet 



2. Granite-gravel, intermingled with small pieces of a substance resembling cliarcoal 



and a few shells, 3 feet. 



3. Fine gravel, mud, and shells, 12 feet. About this depth several beds of oysters, 



4 or 5 feet in thickness, extending irregularly to within 4 or 5 feet of the tin 

 ground. 



4. Closer mud intermingled with shells. In this stratum have been found several 



branches and trunks of trees cut with an axe or sharp instrument, horns, and 

 bones of stags, likewise human skulls. 



5. Tin ground, varying from 1 to 6 feet. The shells correspond with those found 



in the Falmouth Estuary. 



Mr. Eay Lankester informs me that at Antwerp the Black Crag is 

 below the level of high-water, reposing on Eocene Clay. The top of 

 the Yellow Crag is within 20 feet of the level of high water. 



The Cyrena beds of St. Valery and Abbeville are also within 50 

 feet of high- water mark. 



Different opinions prevail as to the relative ages of these Crags, 



