SALTNESS OF THE SEA. 13 



appearance of a sort of mucous sac of about an inch long, which, 

 thrown upon the deck of a ship, emits a light like a rod of iron 

 heated to a white heat. Sir John Herschel noted on the surface of 

 calm water a very curious form of phosphorescence; it was a polygon 

 of rectilinear shape, covering many square feet of surface, and it 

 illuminated the whole region for some moments with a vivid light, 

 which traversed it with great rapidity. 



The phosphorescence of the sea may also result from another cause. 

 When animal matter is decomposed it becomes phosphorescent. The 

 bodies of certain fishes, when they become a prey to putrefaction, 

 emit an intense light. MM. Becquerel and Breschet have noted 

 fine phosphorescent effects from this cause in the waters of the Brenta 

 at Venice. Animal matter in a state of decomposition, proceeding 

 from dead fish which floats on the surface of ponds, is capable of 

 producing large patches of oleaginous matter, which, piled upon the 

 water, communicates, to a considerable extent, especially when the 

 water is agitated, a phosphorescent appearance. 



Whatever may be the case elsewhere, there are local causes which 

 affect the colour of the waters in certain rivers, and even originate 

 their names. The Guainia, which with the Casiquaire forms the Rio 

 Negro, is of a deep brown, which scarcely interferes with the 

 limpidity of its waters. The waters of the Orinoco and the Casiquaire 

 have also a brownish colour. The Ganges is of a muddy brown, 

 while the Djumna, which it receives, is green or blue. A whitish 

 colour is characteristic of the Rio Bianco, or White River, and of 

 many other rivers. The Ohio in America, the Torgedale, the 

 Goetha, the Traun at Ischl and most of the Norwegian rivers, are of 

 a delicate limpid green. The Yellow River and the Blue River in 

 China are distinguished by the characteristic tint of their waters. 

 The Arkansas, the Red River, and the Lobregat in Catalonia, are 

 remarkable for their red colour, which, like the Dart and other 

 English rivers, they owe to the earth over which they flow, or which 

 their waters hold in suspension. 



The water of the sea is essentially salt, of a peculiar flavour, 

 slightly acrid and bitter, and a little nauseous. It has an odour 

 peculiarly its own, and is slightly viscous. In short, it includes a 

 great number of mineral salts, which give it a very disagreeable taste, 

 and render it unfit for domestic use. It contains, among the soluble 

 substances which exist on the globe, principally chloride of sodium, 

 and sulphates of magnesia, of potassium, and of lime. 



