National Geographic : 1948 Sep
Exploring the Mid-Atlantic Ridge toothed peaks-like climbing into the Rockies from the Great Plains of Kansas. What did these hidden mountains look like? Of what kinds of rocks were they made? What sediments covered them? To answer such questions, our expedition had set sail in Atlantis on July 16, 1947. Atlantis is the veteran research vessel of the Woods Hole Oceanographic Institution (page 276). On this ship I had gained most of my experience in scientific work at sea, on a dozen cruises made between 1935 and 1945. She is a 146-foot steel-hulled ketch, built in Copenhagen in 1930-31 especially for oceano graphic work. Diesel engine and 7,200 square feet of canvas give her a cruising range out of all proportion to her size. Her speed, how ever, is limited to about ten knots. More Crowded than a Submarine Two good-sized laboratories occupy the choicest space on the ship, for science comes first and comfort second. Living space, fur ther restricted by the big winch in the hold and the smaller winch on deck, was even more crowded than that on a submarine. We car ried a crew of 18 headed by Capt. A. K. Lane, late of the U. S. Coast Guard, and 10 assorted scientists, some of whom slept on deck in good weather to relieve the congestion below. After two days of sun and bright blue sea, the little ship hit heavy weather. When she struck a big sea at just the wrong angle, she seemed to stop dead. Soon, however, the skies cleared, an occa sional silvery flying fish landed on deck, and between oceanographic duties some of the men took a dip over the side in 80° water, keeping a wary watch for sharks and the big poisonous jellyfish called Portuguese man-of war. We were in the Gulf Stream. Dr. Lyman J. Briggs, Chairman of the Re search Committee of the National Geographic Society and former Director of the National Bureau of Standards, accompanied us as far as Bermuda. He was an inspiring shipmate. On our second day out we made our first water temperature and salinity measurements, the 3,603d such Hydrographic Station made from Atlantis during her 17 years of oceano graphic work. Each is insignificant in itself, like individual weather-station observations, but all form part of a great picture which gives man better understanding of the waters, winds, and weather of his globe. Bottles for collecting water samples for chemical analysis were fastened at intervals to a wire and lowered over the side. When the bottles were at the desired depths, a small weight called a messenger was sent sliding down the wire, causing all the bottles to close. Deep-sea thermometers attached to each bottle were inverted at the same time. break ing the mercury thread in such a way that the water temperature could be read upon return to the surface (page 292). A dozen or so bottles are usually lowered at a time to learn how cold and salt is the water at as many different depths. Creatures of Darkness Sink by Day At the same time we generally made net tows to learn the concentration, at various depths, of the tiny plants and animals called plankton. Some of these organisms spend their life in perpetual twilight, going down by day to avoid the light and coming up near the surface at night. We towed our silken nets for them every night at 2 a.m. So incredibly numerous are such sea crea tures that this layer of ocean life actually returns an echo of the sound sent down by the Fathometer. The echo from this so-called "scattering layer" is sometimes so strong that it causes navigators to think they are sailing over a shoal (page 290). Five days after we left Woods Hole, At lantis tied up to a mooring in St. George's Harbour, Bermuda, being denied the privilege of docking because of the ton of TNT we carried for scientific use. When this was re moved to a storage magazine next day, At lantis was welcomed into polite society. Our approach to Bermuda and our depar ture were depicted strikingly on the trace of the recording Fathometer. It revealed the island as a great submarine mountain rising abruptly from the depths of the ocean. This majestic topography showed itself as clearly asifwehadbeenflyingoveritonadayof good visibility. Sea Mount Tells Surprising Story Northeast of Bermuda, on our way to the Ridge, we investigated a sea mount found in 1945 by the U. S. Navy destroyer escort Muir while making a transatlantic passage to drop bombs to be heard by our Navy's SOFAR station in the Bahamas.* * SOFAR (Sound Fixing and Ranging) was in vented by Dr. Ewing during World War II while working at the Woods Hole Oceanographic Institution under a contract with the Bureau of Ships, Navy Department. It is based on the fact that a small bomb fired at the right depth (2,000-4.000 feet) may be heard by hydrophones, also at the right depth, even across the entire width of an ocean. By triangulation, the spot at which the bomb is exploded can be deter mined within about a mile. One of the practical uses of SOFAR is location of aviators forced down at sea.