(19th-195s)

During this period, the world's marine exploration activities are increasing day by day, and the research in the field of oceanography has made great progress in depth and breadth, and has become a discipline independently. This period can be divided into two major stages: Challenger stage and Meteor stage.

"Challenger" stage is usually called "Challenger" era, including the whole 19th century. At this time, marine scientific investigation developed from individual to comprehensive, and oceanography began to take shape gradually. The most important event at this stage is the British "Challenger" expedition, as well as the "Forward" Arctic Sea expedition. From the early 19th century to 1872. At this time, the investigation was different from the maritime exploration in the first period, and it was clearly based on marine scientific investigation, but it was often based on individual and single disciplines. The more important investigations and achievements are as follows:

① The British "Beagle" explored the world from 1831 to 1836. It lasted five years and experienced the Atlantic Ocean, Indian Ocean and Pacific Ocean. C.R. Darwin, a British scientist and evolutionist, participated in the expedition. According to the data obtained from this expedition, Darwin explained the origin of coral reefs, put forward a discussion on seabed movement, and published the Origin of Species in 1859. The information obtained from this expedition was compiled by F. Roy and Darwin, the captains of the Beagle, into the Report on the Navigation of the Beagle (4 volumes).

② British J.C. Ross explored Antarctic waters from 1839 to 1843. Ross measured a depth of 2,425 fathoms (about 4,438 meters) in the sea at 27 16' S and 17 29' W, which set a record for deep-sea sounding at that time. At the same time, Ross found the same benthic organisms as those found by J. Ross in the North Atlantic a few years ago in the Antarctic waters, thus putting forward the conclusion that the bottom water of the whole ocean has the same characteristics. J.C. Ross also discovered the south magnetic pole.

③ From 1842 to 1847, Captain M.F. Murray of the United States Navy systematically studied the ocean winds and currents, and made charts according to these records. In 1855, he published Marine Physical Geography, which provided people with the first oceanographic classic. The first bathymetric map of the North Atlantic basin was published in 1854, which provided a scientific basis for laying submarine cables in the Atlantic Ocean.

④ E. Forbes, the founder of British marine biology, made many investigations and studies on the creatures in western Europe, southern Europe and North Africa. He divided the Aegean Sea into eight zones according to different depths and put forward the concept of zoning of marine life distribution for the first time. It is considered that the deeper the depth, the less organisms there are, and the zone below 55 meters is an inanimate zone. In 1836, C.G. Ellenberg discovered that many rocks in the European continent contained marine life remains such as diatoms, sponges and radiolarians. He believed that a large number of organisms deposited on the seabed was the reason for the formation of these sedimentary rocks, and pointed out that such sediments were still forming. In 186, Bulldog found a large number of corals and molluscs on the cable salvaged from the depth of 22m in the Mediterranean Sea. This discovery broke Forbes' conclusion that there is no biological zone below 55 meters in the sea. In 1868, the British "Lightening" collected a large number of creatures at a depth of 1,1 meters in the sea between shetland islands and the Faroe Islands. From 1869 to 187, the British Porcupine sampled 16 times in the deep water of 18 ~ 4464 meters in the west of Ireland, the Bay of Biscay and the Faroe Channel, and obtained quite a lot of creatures each time, especially sea urchins that were considered extinct after Cretaceous. In 1872, C.W. Tang Musun wrote the authoritative oceanographic work Deep Sea based on the investigation results of Lightning and Porcupine.

⑤ After 195s, the laying of submarine cables promoted the survey of ocean sounding. In 1856, the special survey ship "Archick" carried out sounding between the east coast of North America and the west coast of Ireland, confirmed the existence of the central ridge of the North Atlantic, and suggested laying submarine cables along this ridge. In 1857, "Cyclops", 1858 and 186, "Gorgon" and "Fighting Dog" successively conducted bathymetric surveys in the North Atlantic. With the support of the Royal Society, C.W. Tang Musun set sail in December 1872 and returned in May 1876, sailing more than 12, kilometers in three and a half years. Sounding, temperature measurement, water collection, sampling and trawling were carried out at hundreds of stations in the Pacific Ocean, Atlantic Ocean, Indian Ocean and Antarctic Sea, and a large number of marine biological samples, sediment samples and seawater samples were collected. This voyage collected many specimens of exotic animals in the deep sea, including animals below 55 meters in the northern waters of the Hawaiian Islands, and measured the depth data (818 meters) of the Mariana Trench in the Pacific Ocean. Challenger's expedition not only initiated the era of comprehensive marine survey, but also obtained very rich marine data. Dozens of scientists have devoted themselves to studying for more than 2 years before completing the compilation of the investigation report, which consists of 5 volumes and more than 29,5 pages, laying a solid foundation for the establishment of oceanography. In marine life, more than 4,4 new species have been discovered, providing knowledge of marine zoology from the surface to the seabed. In marine geology, important achievements are the discovery of deep-sea ooze and red clay, and the collection of manganese nodules. In marine physics, in addition to investigating ocean currents and meteorology, the main achievements are as follows: ① According to the results of geomagnetic measurement, the deviation of navigation compass was mastered; ② Drawing the contour map; (3) It is found that the water temperature below 18 meters is not affected by the season, and the temperature changes very little; ④ It is considered that the water temperature at the ocean bottom is basically the same in a large range, but it also shows specific values in different sea areas; ⑤ The accurate locations of islands and dangerous rocks are determined. In the aspect of seawater chemistry, W. dietmar made a comprehensive and complete analysis of seawater, which theoretically confirmed the principle put forward by J. G. Forchhammer in 1865 that the relative contents of its main chemical components are constant regardless of the absolute value of the salt content in seawater. Before the observation of Challenger, it was generally believed that the proportion of deep sea water was very large, and the heavy objects thrown into the sea would not sink to the bottom of the sea. The "Challenger" expedition denied this argument.

Challenger's expedition aroused the upsurge of ocean exploration in various countries. The German Antelope (1874 ~ 1876) and the Russian Warrior (1886 ~ 1889) made global expeditions, the Austrian Polar (189 ~ 1898) made expeditions in the Red Sea and the Mediterranean Sea, and the American Black. From 1925 to 1927, the German research ship Meteor made a survey of the South Atlantic for two years and three months, which was another epoch-making scientific survey after the British Challenger. This expedition is based on marine physics, adopting various electronic technologies and modern scientific methods, and is famous for its accurate observation. It used electronic echo sounder for the first time and obtained more than 7 thousand ocean depth data; For the first time, the undulating outline of the ocean bottom was clearly revealed; The basic situation of ocean circulation and ocean heat and water balance is revealed. Sixteen volumes of investigation reports were published, including seabed, marine physics, marine chemistry, marine biology, marine meteorology, and internal wave observation.

In p>1929～1935 and 1937-1938, Meteor also conducted surveys in Iceland and the northeast Atlantic Ocean respectively, and found out the complex sea conditions in the polar peak zone. Through repeated synchronous surveys in several countries, the continuation of the Gulf Stream is clearly drawn. In order to further study the deep-sea creatures, the Danish research ship Galathea conducted a marine survey in the Zhou Hang world from October 195 to September 1952. When sampling at the bottom of the sea, the expedition used a 12,-meter-long steel wire rope to collect a large number of living microorganisms from the bottom material of the Philippine trench more than 1, meters deep. In July, 1951, white anemones, beautiful red shrimps, lightfish, jellyfish, nereis, etc. were collected on the seabed rocks at a depth of 1,19 meters and in the nearby waters, which proved that creatures also inhabited at a depth of 1, meters. A large number of black fish, blue-white starfish, sea cucumbers, shrimps, long-legged crabs and other precious creatures have been collected from the deep sea of 3,4-7,2 meters, and a living fossil "Neopilina" that people think has long been extinct has also been collected. According to the collected samples, they found that the ultra-deep-sea animals living at a depth of more than 7, meters can adapt to the huge water pressure, which is different from the animal species from the sea area and continental slope at a depth of 2,-3, meters. In this expedition, the primary productivity of marine organisms was measured by 14C method for the first time, and the deep-sea geomagnetism was also measured. The Soviet "Warrior" visited the Pacific Ocean from 1949 to 1958. The "Warrior" (витязь) mainly visited the Pacific Ocean. "Warrior" carried out bathymetry during the inspection, corrected the bathymetric map of the offshore of the Far East and the Pacific Ocean, and found some fault zones, submarine mountains and seamounts. It was found in Mariana Trench that the world's deepest Challenger Sea is 11,34 meters. A deep-sea abyss (1382 meters) was discovered in Qiandao-Kamchatka Trench. During the investigation, a 4-meter-long submarine columnar sample was obtained, and the geological history of 1 million years was analyzed and studied. It is found that deep water is constantly flowing, and a strong laminar flow with a speed of up to 3 cm/s is measured at a depth of 1 ~ 3 meters. The strong vertical mixing of deep seawater and the vertical movement of plankton on a scale of several kilometers are clarified. The survey results show that there are also many kinds of creatures in the deepest trench with a depth of 1 thousand meters. After 1959, the "Warrior" was still engaged in inspections in the Indian Ocean. Other expeditions at this stage include Carnegie, Nautilus, Baird and Horizon of the United States, Maud of Norway, Gauss of Germany, Dana-I and Dana-II of Denmark, Frenchmen and Pass of France, and the United Kingdom. Main Achievements On the basis of marine investigation, many achievements have been made in oceanographic research and theory. For example, Archduke Albert I of Monaco's Ocean Bathymetric Chart (194), V.W. ekman's Wind Current Theory (195), A.L. Wegener's Continental Drift Theory (1912), A.Holmes's Mantle Convection Theory (1929), and W.M. Ewing made the first ocean earthquake. J.P. Jacobsen and M.H.C Knudsen put forward a new definition of seawater chlorine (1937), H.H. Hess discovered the submarine Pingdingshan (1946), C.E. Zobel published Marine Microbiology (1946), H.U. Sverdrup's ocean circulation theory (1947), H. Among them, the magnum opus Ocean (1942) written by Sverdrup and others comprehensively and profoundly summarized the achievements of this stage.