54 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



spreading of the cold bottom water from the poles. No bottom 

 temperature was obtained as low as the freezing point of 

 salt water. 



(5) . The determination of the exact position of many islands 

 and rocks, the longitude of which had been previously uncertain. 



(6). The charting and surveying of various little known 

 parts of the world, and their biological investigation. 



(7). The determination of the ocean currents both on 

 the surface and at various depths. 



One of the results of the £< Challenger " expedition was 

 undoubtedly an increase in our knowledge of the details of 

 structure and the probable mode of formation of coral reefs 

 and islands. Before the expedition, several geologists and 

 naturalists had published doubts as to the universal applica- 

 bility of the subsidence theory of coral reefs which we owe 

 to Darwin. Semper, for example, showed that in the Pelew 

 Islands up-raised reefs and atolls (which according to the 

 theory indicate a sinking area), are found close together. 

 The " Challenger " observations in regard to submarine 

 elevations and the mode of accumulation of deep sea deposits 

 enabled Mr. Murray (afterwards Sir John) to formulate and 

 publish a new theory as to the origin of atolls, which does 

 not postulate any changes of level, but makes use merely 

 of processes of growth and decay which we know to be at 

 work and constantly acting. The matter is by no means 

 finally settled even now, and it may well be that Darwin's 

 theory holds good in certain parts of the ocean while Murray's 

 explanation is true for other series of atolls. 



One of the principal additions to knowledge made by 

 the " Challenger " observations was as regards the deposits 

 now accumulating at various depths on the floor of the ocean. 

 During the voyage the preservation and examination of 

 these deposits was part of Murray's work, and subsequently, 

 along with his friend the Abbe Renard, he made a most 

 comprehensive study of all the submarine deposits (about 



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