358 



SCIENTIFIC RECREATIONS. 



contains many salts; its composition is as follows, according to Dr. Schweitzer, 

 of Brighton : 



Water 



Chloride of sodium (salt) . 

 Chloride of potassium i 

 Chloride of magnesium 

 Bromide of magnesium 

 Sulphate of magnesia 

 Sulphate of lime .... 

 Carbonate of lime .... 

 (With traces of iodine and ammonia). 



96474372 grains. 



28-05948 



076552 



3-66658 



0-02929 ., 



2-29578 ., 



0-40662 ., 



0-03301 



looo'ooooo grains. 



Fig. 349. Stalactite Cavern. 



There is much more oxygen in water than in air, as can be ascertained 

 by analysis of these compounds. This great proportion in favour of water 

 enables fish to breathe by passing the water through the gills. Marine 

 animals (not fishes), like the whale, which is a warm-blooded creature, and 

 therefore not suited to exist without air, are obliged to come to the surface 

 to breathe. The density of salt water is much greater than that of fresh 

 water, and therefore swimming and flotation is easier in the sea than in a 

 river. We shall have more to say of water by-and-by. 



