14 A WONDERER UNDER SEA 



Earth leveled off, the dry land would wholly disappear 

 and an unbroken waste of waters, a mile deep, would 

 stretch from pole to pole and around and around the 

 equator. Such a thought makes a rowboat a trifle more 

 comforting than Mount Everest. 



Mention of the sea as an old home of ours Is not a figure 

 of speech. Perhaps the most dramatic and amazing thing 

 about our human body is one certain proof of this former 

 aquatic life and even a hint as to the actual time when 

 some dim ancestor of ours crawled out upon land. When 

 the ocean first came to be, say a billion and a half years 

 ago, its waters were fresh, but at once they began dissolv- 

 ing salts and other minerals from the adjacent land. Then 

 clouds and rain and rivers were born and thousands of 

 tons of ingredients began to be washed down. So today 

 the ocean is very slightly Salter than it was yesterday, and 

 the lowlier creatures who live in it and have open cir- 

 culations have, of course, salt water for blood. It simply 

 flows in and through them and out again, leaving a bit of 

 oxygen and taking away some waste matter. But very 

 long ago some ancient animal closed up its system of veins 

 and arteries and from a water-drenched primitive became 

 a self-sustaining, gilled creature. And from this minute 

 on, the water in which it swam kept getting salter and 

 Salter, while the composition of its blood remained the 

 same. 



A human being can drink fresh but not salt water; 

 fresh water injected into the veins is a potent poison, while 



