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 Greenland. This is the path of one of the great Arctic return-currents.
Fig. 6.
Ball's Dredge.
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 ems 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 becoming 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."
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 Müller, 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
