OCEAN WATERS 



153 



When the river waters run into the sea, they carry with them 

 whatever they have dissolved from the land. When the 

 water of the sea evaporates and is borne away, to fall upon 

 the land again, the dissolved 

 material is left behind in 

 the ocean. 



Thus the sea has for all 

 time been receiving soluble 

 contributions from the land. 

 It is easy to prove that it 

 contains salt, for we can 

 taste it. It must contain "AIRING" AN AQUARIUM 



Fishes may die in the still water of an 

 aquarium for lack of fresh air. The 

 small stream from the tube stirs up 

 the tank-water and causes it to 

 absorb air. 



lime, since coral and shell 

 animals of the sea depend 

 upon it for the hard parts 

 of their bodies. There must 



be organic food material in it, or else fixed animals like 

 corals could not get their food. It contains air, for with- 

 out air fishes could not breathe. These are the principal 

 substances which we need consider in the study of ocean 

 water, but the chemist can find many other substances 

 dissolved in it. There is so much dissolved 

 material of different kinds in it that the density 

 of the solution is sufficient to keep ocean water 

 from freezing until it reaches 28 F., instead of 

 32 F., the temperature at which fresh water 

 freezes. 



Experiment 72. Place in a deep dish of fresh 

 FIGURE 78 water a density hydrometer (Figure 78), or stick 

 loaded with lead at one end so that it will float up- 

 right. Mark with a rubber band the depth to which the hydrom- 

 eter sinks in the water. Now place the hydrometer in sea 



