ANIMAL LIFE IN WATER 



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hollow space, the dish begins to sink. The depth to which 

 it sinks may be regulated by the amount of water admitted. 

 Submarines are boats so constructed as to be water-tight 

 even when submerged. Special compartments are provided 

 to which water can be admitted and from which it can be 

 driven out. When the commander of a submarine wishes to 

 submerge his vessel, he gives the order to admit sufficient 

 water to the compartments to make the submarine heavier 



U. S. official 



A SUBMARINE SUBMERGING 



than an equal volume of water. It therefore sinks. In order 

 to make the submarine rise, the operators must force water 

 out of the tanks until the submarine displaces a weight of 

 water greater than its own weight. It will then rise and 

 float partly submerged. If just enough water is admitted to 

 the tanks to make the weight of the submarine equal to the 

 weight of the water displaced, the submarine can be made to 

 float at varying depths. 



Animal Life in Water. From previous experiments we 



