PRESSURE OF THE WATERS. 387 



of fresh 'water, closely corked, into the ocean, 

 when it has been found that the corks have 

 been driven in, while the fresh water has been 

 replaced ,by salt, or the bottles have burst with 

 the enormous pressure to which they were thus 

 subjected. Pieces of light porous wood have 

 been weighted and sunk, and when brought up 

 again have been found to be so 'condensed in 

 their tissues, as to be incapable of floating any 

 more, sinking like stones when thrown back 

 into the water. In the experiments undertaken 

 by various observers upon the temperature of 

 the deep sea, by sinking thermometers, acci- 

 dents repeatedly occur from the pressure of 

 the waters above. What sailors term " water- 

 logged " occurs when a boat or vessel has been 

 sunk beneath the surface so low as to cause 

 the pressure of the superincumbent water to 

 drive the particles of water into its inter- 

 stices. Mr. Scoresby mentions that, during a 

 whaling cruise in the Arctic regions, a whale, 

 on being harpooned, dragged the boat under 

 water, the crew escaping on to a piece of ice. 

 When the fish returned for air to the surface, 

 it was again struck, and then killed ; it imme- 

 diately began to sink. Fortunately, a grapnel 

 was thrown over its tail, and its descent was 

 thus arrested, though at imminent risk to the 

 boat. On hauling up the line, it was found 



