336 Spencer — Improbability of Land at the North Pole. 



the continental shelf has a breadth of 300 or 350 nautical miles 

 (see map). Its outer margin is at a depth of 300 feet, beyond 

 which is the rapid descent of the continental slope. In front 

 of Spitzbergen, and apparently adjacent to Franz Joseph archi- 

 pelago, the shelf has a breadth of only about 30 miles. Its 

 border recedes and forms an embayment east of Novaya 

 Zemlia. North of the New Siberian Islands, Nansen found 

 that the submergence of the continental slope increased from 

 about 300 feet to 6000 feet in 30 miles. A similar gradient 

 has been found adjacent to Spitzbergen. Soundings in suffi- 

 cient numbers have been taken to establish the existence of the 

 broad shelf, with a few others suggesting its border, as for 

 instance, where in proceeding outward the sea suddenly deepens 

 from 300 feet to 700-800 feet. Thus defined, Hansen's map 

 shows a direct line in front of Bering Straits to north of Alaska. 

 Here the continent encroaches upon and greatly contracts the 

 shelf, — an important analytical feature. The shelf appears to 

 be reduced to a breadth of perhaps 40 miles. The Arctic basin 

 does not approach Bering Straits, which is only a shallow 

 lateral trough from the basin itself, but ends in Beaumont Sea, 

 between Prince Patrick's Land and Alaska, where the Mac- 

 kenzie River, after passing through its own broad embayment 

 or delta, extends to a submarine valley discovered, so far, to a 

 depth of over 1140 feet beneath sea level, thus deeply incising 

 the shelf. In the broad channel between Bank's and Baring 

 Lands and the continent, which ( unless it is otherwise named, 

 and the charts do not show it ) might appropriately be called 

 Richardson Sound, after its explorer (1848), the submarine val- 

 ley has a depth of 1836 feet, near the head of a branch fjord, 

 at a point 175 miles within the line of the islands. 



Lower down the sound are a number of deep soundings, but 

 they do not reach the bottom in the central axis. Beyond, 

 in McClure's Strait, which separates the eastern side of Bank's 

 Land from Melville Island, the fjord attains a depth of 1362 

 feet and more, at a point 200 miles within the line of the 

 islands. Here we have found the evidence of deep submarine 

 valleys or fjords entering Beaumont Sea from three different 

 directions, and very much deeper than the submergence of the 

 great continental shelf of the Arctic basin. Further proof is 

 not needed to establish the fact that Beaumont Sea is a broad 

 profound valley leading to the Polar basin, though the depth is 

 not known. Also, that the continental shelf is deeply chan- 

 nelled by the valleys. Now, as we have learned from the 

 analysis of the submarine valleys or fjords off Norway and 

 both coasts of America, the border of the continental shelves 

 does not usually exceed a distance of more than from 40 to 

 100 miles beyond the outer line of the land or islands. Off 



