The Mighty Deep 



they black with midnight darkness ? or do faint 

 glimmers of daylight creep through ? 



Ocean-water, like other water, is transparent. 

 Any substance is transparent, when thin enough, 



even gold. A very thin film of water is not, 



however, needed for transparency. Many feet, 

 even many yards, may be seen through, if clear 

 and pure. Few of us have not, at one time or 

 another, looked down from a boat, to see golden 

 sand, variegated pebbles, small fishes swim- 

 ming about, at a considerable depth. 



Thus with water, as with denser materials, 

 transparency is merely a question of thickness. 

 As the thickness increases, more and more rays 

 of sunlight are taken captive, and the water 

 becomes less and less translucent, till at length, 

 if we could get deep enough, we should find 

 ourselves to be surrounded with blackness. 



Another feature of ocean-depths is that of 

 immense pressure. 



We bear a certain degree of it in that other 

 and lighter ocean — the Atmosphere. A man 

 of medium size has upon his body about thirty 

 thousand pounds' weight, or some fifteen pounds 

 to the square inch. But this is nothing to what 

 he would have to endure down in ocean-waters. 

 At a depth of one mile, an extra ton would 



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