THE PHYSICAL CONDITIONS OF THE ABYSS 29 



all in the temperature of a column of water that has 

 had time to settle, the thermometer will always reach 

 its highest point at the top of the column and its 

 lowest at the bottom, for the colder particles being 

 of greater specific gravity than the warmer ones will 

 sink, and the warmer ones will rise. 



The truth of this will be clear if we imagine a 

 locality at the bottom of a deep ocean with a source 

 of great heat such as an active volcano. 



Such a source of heat would, it is true, raise the 

 temperature of the water in its immediate vicinity, 

 but the particles of water thus heated would im- 

 mediately commence to rise through the superjacent 

 layers of colder water, and colder particles would fall 

 to take their places. Thus the effect of an active 

 volcano at the bottom of the deep sea would not 

 be apparent at any very great distance in the same 

 plane. In fact, unless the bottom of the ocean was 

 closely studded with volcanoes we should expect to 

 find, as indeed we do find, that the temperature of 

 the sea rises as the water shallows. 



If then we were to consider a great ocean as 

 simply a huge basin of water, we should expect to 

 find the water at the surface warmer than the water 

 at the bottom. The temperature of the surface 



