To get the most accurate possible temperature 

 reading of deep water, De Saussure coated 

 a tiiermometer bulb with wax, then placed 

 the device in a wooden box to prevent too 

 much movement of water. He then left the 

 device in deep water for twelve hours. 



The development of underwater acoustic methods during the 

 First World War stimulated new interest and advances, and it was 

 not long before we had echo sounders able to record a continuous 

 profile of the deep ocean floor as the ship crossed the ocean above 

 it. Some of the older scientists were not very enthusiastic about 

 this new method, because at first it tended to cut off" the supply of 

 samples of bottom sediments produced by the wire soundings, but 

 the interest and progress awakened by the new profiles soon 

 brought more extensive and specially planned sampling and coring 

 programs. We now know quite a lot about a few small areas of the 

 sea floor, but there are many large areas about which we know 

 little or nothing. 



The more inquisitive of later sea explorers began to take an 

 interest in the temperature of the deep sea almost as soon as reliable 

 thermometers were invented. The first record of any measurements 

 at great depths is that of Captain Henry Ellis' observations in 1749 

 at depths of 650 and 891 fathoms, north of the Cape Verde Islands. 

 He used a stout wooden barrel, about the size of an ordinary pail, 

 with top and bottom valves which stayed open while the sampler 

 was being lowered but which closed while it was being brought 

 up. It was hauled up as fast as possible so that the temperature of 

 the water inside would not have much time to change. 



George Forster made three such series of deep measurements 

 during Captain Cook's circumnavigation. One of them made in 

 Antarctic waters southeast of Cape Town is remarkable because it 

 showed a warm undercurrent moving south and replacing the 

 outward spread of cold water at the surface. The fact that Forster 

 made only three sets of observations in three years suggests a lack 

 of opportunity. Captain Cook, like most practical seamen, may not 

 have had much time for what might have seemed to him rather 

 pointless enquiries. He did not try to sound the oceans, only the 

 approaches to the land. William Scoresby, the whaling explorer 

 and scientist, also used wooden samplers, but he found that they 

 did not stand up for very long to the soaking up of water at high 

 pressures, so he made metal containers coated with insulating 

 material. 



Not all the temperature measurements depended on attempts to 

 haul insulated water samples to the surface. H. B. de Saussure, the 

 great Swiss mountain cUmber, used an alcohol thermometer with 

 its bulb insulated with a three-inch mixture of wax, resin, and oil 

 to measure the temperature at a depth of 3 20 fathoms ofi" Nice. He 

 left it down for twelve hours, pulled it up as fast as possible, and 

 estimated that his reading was correct to within a fraction of a 

 degree. 



Maximum and minimum thermometers promised to make the 

 task of measuring deep temperatures much easier, but at first the 

 effect of pressure on the thermometer bulb was overlooked. The 

 thermometers used by Sir James Clark Ross read about i°c. too 

 high for every 500 fathoms because the mercury was squeezed this 

 much up the stem by the pressure on the bulb. At about 50° S. 

 latitude in the Antarctic Ocean, where the temperature at the surface 

 is about 4°c., and at the bottom in 2000 fathoms o°c., Ross found 

 4°c. all the way down. He accepted the idea previously put forward 

 by the French Admiral Dumont d'Urville that the deep ocean 

 basins, like the bottom of deep, fresh-water lakes, were filled with 



178 



