THE BEITISH SEAS. Ô 



Glaciers are no longer stranded on its shores, but rivers deposit in it the sediment 

 with which they are charged, whilst the arctic current, which makes itself feebly 

 felt in this vast gulf, conveys into it the pumice-stone ejected from the volcanoes 

 of Iceland and Jan Mayen.* Deposition is consequently still going on, though at 

 a much slower rate than formerly. But how are we to explain the gradual filling 

 up of the North Sea, whilst the abyssal channel which separates it from Norway 



Fig. 2. — The Strait of Doyeb axd the Exglish Chaxxel. 

 Prom an Admiralty Chart. Scale 1 : 795.000. 





10 Maes. 



retains its depth of hundreds of fathoms ? Is it not that its very depth saved 

 it from becoming the depository of glacial drift ? The glaciers carried south- 

 ward by currents and northerly winds may be supposed to have stranded only 

 after they had reached the shallower waters of the North Sea, when, melting 

 under the influence of the sun, they deposited upon its bottom the débris they 

 carried. 



The Strait of Dover, which joins the North Sea to the English Channel, has a 

 width of only 20 miles, and in depth nowhere exceeds 180 feet. The navigation is 

 * "Annales Hydrographiques," 4e trimestre, 1873. 



