264 



THE POPULAR SCIENCE MONTHLY. 



Fig. 5. 



water in the Spitzbergen Sea, a trough 500 miles wide, and, in some 

 places, nearly 12,000 feet deep, curves along the east coast of Green- 

 land. This is the path of one of the great Arctic return-currents. 



After sloping gradually to a depth of 

 3,000 feet to the westward of the coast 

 of Ireland in latitude 52, the bottom 

 suddenly dips to 10,000 feet at the rate 

 of about 15 to 19 feet in the 100; and 

 from this point to within about 200 miles 

 of the coast of Newfoundland, when it 

 begins to shoal again, there is a vast 

 undulating submarine plain, averaging 

 about 12,000 feet in depth below the 

 surface the ' telegraph plateau.' 



" A valley about 500 miles wide, and 

 with a mean depth of 15,000 feet, 

 stretches from off the southwest coast 

 of Ireland, along the coast of Europe, 

 dipping into the Bay of Biscay, past the 

 Strait of Gibraltar, and along the west 

 coast of Africa. Opposite the Cape de 

 Verde Islands, it 6eems to merge into a 

 slightly deeper trough, which occupies the 

 axis of the South Atlantic, and passes 

 into the Antarctic Sea. A nearly similar 

 valley curves around the coast of North 

 America, about 12,000 feet in depth, off 

 Newfoundland and Labrador, and be- 

 coming considerably deeper to the south- 

 ward, where it follows the outline of 

 the coast of the States, and the Bahamas 

 and Windward Islands, and finally joins 

 the central trough of the South Atlantic off the coast of Brazil, with 

 a depth of 15,000 feet." 



Ball's Dredge. 



Until within a hundred years but little was known of the living 

 inhabitants of the deep sea, except the few objects that adhered to 

 lead-lines, or were taken accidentally by fishermen in trawls and 

 oyster-dredges ; and, as odd things of no market value were generally 

 thrown away, the knowledge from this source increased but slowly. 

 The first dredge used by a naturalist to collect specimens from the 

 sea-bottom was employed by Otho Friedrich Mtiller, who published a 

 quaint book about it in 1779. His dredge was a square-mouthed bag 

 (Fig. 4), and he does not appear to have used it beyond a depth of 

 180 feet. The dredges now used by naturalists are modifications of 

 the oyster-dredge, which is described as a light frame of iron, about 



