TWO REMARKABLE DISCOVERIES IN THE PHYSICAL GEOGRAPHY OF THE SEA.

New Zealand Times, Volume XXIX, Issue 4291, 21 December 1874, Page 3

TWO REMARKABLE DISCOVERIES IN THE PHYSICAL GEOGRAPHY OF THE SEA.

(From the JVew York Herald, September 25.) Two important expeditious, now engaged in oceanic research, one in the Atlantic and one in the Pacific, have recently reported some of the results of their labors, which will probably put a new phase on the great problem they are seeking to elucidate. We have very lately published the full account of Commander Belknap’s extensive survey of the bottom of the Pacific lying north of the great equatorial current. While his aim lias been specifically to test the telegraphic accommodations of the North Pacific bed, his soundings reveal an important principle never fully, if at all, known to physical geographers. When about a hundred miles south-east of Sendai Bay, on the east coast of Japan and directly in the strong sweep of the Ku’ro Siwo or Japan current, the sounding indicated abyssal depths, while a little further northward, on the great circle route from Yokohama to Puget Sound, the sinker carried the wire to the astounding depth of 4643 fathoms without reaching bottom, “The tooth of running water is very sharp” is an axiom of physical geography, which, in the curve of the great Pacific Gulf Stream, might well have occurred to the explorer. And he rightly concludes that his experiment “ confirmed the existence of a very deep trough under the Japan stream similar to that out by the Gulf Stream on our own coast.” The discovery that these enormous “rivers in the ocean” carve their channels through the solid basiu of the great oceans is very suggestive to the physicist. It is known that they do not extend to the bottom, the deep sea thermometer ever assuring us that the warm strata cease long before the floor of the ocean is reached. It would seem, therefore, to follow, from the facts brought to light, that these two hot gulf streams act upon the - underlying cushions of cold water and by mechanical impact cause the abrasion or erosion of the bottom over which they run. It is by no means inconceivable that the restless on-flow-ing surface currents, by imparting their own motion to the subjacent water, make their impression on the oceanic floor itself, much as tho constant running of the railway train imbeds the rails in the sleepers of the track and the sleepers in the road bed. This, at least, seems to be the meaning of the striking phenomenon discovered by the explorers in the Western Pacific. The latest reports from Captain Davis, of the Challenger expedition, present a yet more astonishing and a most instructive discovery, likely to revolutionise the whole theory of marine circulation, and putting an effectual quietus on tho interminable theorizings of Dr. Carpenter and his verbose school. The Challenger’s thermomotric surveys of the Atlantic are so numerous and exact that they afford data for constructing a better map of the Atlantic sea bed than we had of North American orography at the beginning of this century. The contour of the North Atlantic presents an irregular belt, shaped like the letter- S reversed, exceeding twenty-five hundred fathoms in deptl), from very near the coast of the United States and the Bahamas toward the African coast between the Canaries and Cape Yerde Islands. North of this lies a submarine bank, rising to within less than two thousand fathoms of the surface, and stretching from Greenland to the Azores. It has always been supposed that over this section poured a cold stream of Arctic water on its way southward, slowly warming as it neared the equator. But the Challenger's soundings prove the startling fact that (beneath the water immediately affected by the sun’s rays, believed not to extend more than eighty fathoms) all the water in the North Atlantic, as far north as the fortieth degree of latitude, is actually warmer than at the same depths under the equator itself ! Such a discovery wan never suspected, and only the unerring and inexorable register of the deep-sea thermometer could have suggested such an apparent anomaly. What is the solution ? There being bottom water of a temperature of thirty-two degrees four minutes at the equator, with wanner water at all stations to the north of it, Captain Davis, of the Challenger, argues, with great sagacity, that it proves unmistakably that tho bottom cold water of the North Atlantic comes from the Antarctic region, and not from the Arctic. Certainly, if at the equator the bottom water supplied from the southward retains its cold so tenaciously, the bottom water of tho North Atlantic, if supplied from tho nearer Arctic region, should ho at least as cold. But the bottom temperature increases decidedly as we go north of the Line, showing that the vast submarine drift from the Antarctic flows over tho Atlantic floor across the equator and penetrates our hemisphere at least as far as forty degrees north. This fact apparently upsets nearly all the prevailing theories, if not every theory that has ever been current, and demonstrates that the circulation of the sea is not carried on between tho Polar and Equatorial basins, but between the Antarctic Ocean and tho North Atlantic on the one hand, and probably, between the Antarctic and North Pacific on tho other. In a word, it shows that the circulation is between two points in opposite hemispheres, and not between the Poles and Equator. The plausibility of this explanation is especially obvious in tho great ocean (from Bellring Strait to the Australian and tho extreme austral latitudes) which is cut off from free -access to the North Pole by the Behring Narrows. If the Challenger figures demonstrate it for tho Atlantic there can he little doubt, that it will he more remarkably illustrated when similar themomotric tests are made in tho Pacific, In tho enormous mass of boreal Antarctic water which is now revealed as forcing itself like a submarine wedge into the tropical section of the North Atlantic, have we not a new and sufficient solution of the long-vexed philosophy of tho Gulf Stream ? Have wo not evidence that the upheaval and piling up the surface of water by tho austral deep sea current, now unmasked, is a vmt causa, if not tho true cause, of that mighy outflow from the tropical basin which pours forth its warm flood toward

Ireland, and never ceases till it reaches the North Polar basin ? The results of the Challenger discovery are far reaching, and make the grandest contribution to marine science ever announced. This discovery will be hailed by all true students of physical geography as most promising, and as offering the only key to the mysteries of the ocean.