lO THE OCEAN WORLD. 



the rivers of the earth would require to pour their waters into it for 

 40,000 years, in order to fill the vast basins anew. 



If we could imagine the entire globe to be divided into 1,786 

 parts by weight, we should find approximately, according to Sir John 

 Herschel, that the total weight of the oceanic waters is equivalent to 

 one of these parts. 



The specific density of sea water is a little above that of fresh 

 water, the proportion being as 1,000 to 1,027. The Dead Sea, 

 which receives no fresh water so as to enable it to maintain itself at 

 the same level as other seas, acquires a higher degree of saltness 

 each year: its present density is equal to 1,028. 



The colour of the sea is continually varying, and is chiefly caused 

 by filtration of the solar rays. According to the testimony of the 

 majority of observers, the ocean, seen by reflection, presents a fine 

 azure blue or ultramarine {cczruleum mare). When the air is pure 

 and the surface calm, this tint softens insensibly, until it is lost and 

 blended with the blue of the heavens. Near the shore it becomes 

 more of a green or glaucous tint, and more or less brilliant, according 

 to circumstances. There are some days when the ocean assumes a 

 livid aspect, and others when it becomes a very pure green ; at other 

 times, the green is sombre and sad. When the sea is agitated, the 

 green takes a bro\\Tiish hue. At sunset the surface of the sea is 

 illumined with tints of every hue of purple and emerald. Placed in 

 a vase, sea water appears perfectly transparent and colourless. 

 According to Scoresby, the Polar seas are of brilliant ultramarine 

 blue. Castaz says of the Mediterranean, that it is celestial blue, and 

 Tuckey describes the equinoctial Atlantic as being of a vivid blue. 



Many local causes influence the colours of marine waters, and 

 give them certain decided and constant shades. A bottom of white 

 sand will communicate a greyish or apple-green colour to the water, 

 if not ver}^ deep ; when the sand is yellow, the green appears more 

 sombre ; the presence of rocks is often announced by the deep 

 colour which the sea takes in their vicinity. In the Bay of Loango 

 the waters appear of a deep red, because the bottom is there naturally 

 red. It appears white in the Gulf of Guinea, yellow on the coast of 

 Japan, green to the west of the Canaries, and black round the 

 Maldive group of islands. The Mediterranean, towards the Grecian 

 Archipelago, sometimes becomes more or less red. The White and 

 Black Seas appear to be named after the ice of the one and the 

 tempests to which the other is subject. 



