TOEFL(Test of English as a Foreign Language)托福題庫下載題庫

     In the nineteenth century, oceanography benefited from the new desire to study phenomena on a global scale. Many scientists collected information on the chemical composition, temperature, and pressure of the ocean at various depths and in different Line regions. The difficulty of gathering information about the ocean depths was immense. 

     At first ii was believed that the temperatures in the depths never fell below 4 degrees Celsius, until it was shown that the figures were distorted by the effect of pressures on the thermometers. There was intensive study of tides and ocean currents; and a number of physicists examined the forces responsible for the movements of the water. For example, James Reonell provided the first accurate map of the currents in the Atlantic. 

     Ocean, and the United Slates Coast Survey made extensive studies of the Gulf Stream. The zoologist Edward Forbes argued that no lire existed below a depth of 300 fathoms (about 600 meters) a view widely accepted until disproved by the voyage of the British research vessel HMS Challenger(1872-1876)The HMS Challenger expedition provided valuable information about the seabed, including the discovery of manganese nodules IS that are now being seen as a potentially valuable source of minerals. 

     The first detailed map of the seabed was provided for the Atlantic by the American geographer Matthew F. Maury- He devised new techniques for measuring ocean depths, and his work proved of great value in laying the first transatlantic telegraph cables. He also studied global wind patterns and was able to provide sailors with guides that 20 significantly reduced die time taken on many routes. Some oceanographers believed that the winds were responsible for producing ocean currents such as the Gulf Stream, but Maury disagreed. He argued that they were produced by changes in the density of seawater due to temperature, which Bet up systems of movement between warm and cool regions of the world. Maury believed that the circulation of a warm current would 25 produce ice-free sea around the North Pole, a claim not disproved until Fridtjof Nansen allowed his vessel The Pram to be carded to within a few degrees of the pole in the years 1893-1896.