10 THE OCEAN 



surface. After this time deep-sea soundings 

 became much more frequent and more 

 accurate. 



About the year 1840 Edward Forbes, as a 

 result of researches in the ^gean Sea, came 

 to the conclusion that both plants and animals 

 ceased to exist in the ocean beyond a certain 

 depth, the zero of vegetable life being at a 

 less depth than that of animal life. The zero 

 of animal life he placed at about 300 fathoms, 

 and his views were very largely applied by 

 naturalists to the whole ocean. Investiga- 

 tions subsequently undertaken by Michael 

 Sars, Wyville Thomson, W. B. Carpenter and 

 others on the Atlantic coasts of Europe showed 

 that animal life existed at a depth of one 

 or two miles. 



These and similar researches led to the 

 despatch of the great " Challenger " Expedi- 

 tion by the British Government in the year 

 1872 for the express purpose of examining the 

 physical and biological conditions of the 

 great ocean basins. The " Challenger " had 

 on board a staff of scientific observers, who 

 during a circumnavigation of the world last- 

 ing for three and a half years made continu- 

 ous observations, on the depth, temperature, 

 salinity, currents, animal and vegetable life, 

 and deposits, at all depths throughout the 

 great oceans. The results of this expedition 



