SINKING OF THE CHANNEL, 347 



The valley of the Somme and the coasts of Nor- 

 mandy are also gradually sinking. Already the turf- 

 pits of the valley of the Somme are below the level 

 of the sea. Submerged forests, whose disappearance 

 beneath the waters is proved by positive docu- 

 mentary evidence, exist oft' the coasts of Normandy. 

 The same may be said of the opposite English coasts. 

 The whole of the Channel is sinking. The Straits 

 of Dover, which would become dry land by a slight 

 elevation of the soil, are therefore but little likely 

 to serve as a means of communication between 

 France and the British Isles. There are two reasons 

 to convince us that it must enlarge : first, in con- 

 sequence of the action of the sea on its shores ; and, 

 secondly, on account of the subsidence of the sur- 

 rounding countries. 



5. Two extensive Zones of Subsidence in the Southern Hemispliere 

 — They are separated by a Zone of Elevation — The Fiji Islands 

 have been sinking during 300,000 years. 



Two vast regions are subsiding in the southern 

 hemisphere. One of them comprehends the nume- 

 rous oceanic archipelagos — the Bass Islands, the 

 Society Isles, the Carolinas, Gilbert's Archipelago, 

 Marshall's Archipelago, and others. Its length is 

 more than 8000 miles, and its mean breadth 



