JS'^fural History of the Ocean^ ^c. 133 



ters are' carried'out below. Between the sea of Marmora 

 and the Euxine these currents exist. Similar motions have 

 been observed at the entrance of the Persian gulf: though 

 the existence of counter currents is not well established, 



4. The Gulf Stream. It is characterised by its higher 

 temperature, — its blue deeper than the ocean — its waters 

 more salt — with an atmosphere finer and lighter. It per- 

 forms a circuit of 3,800 leagues in two years and ten months. 

 The anecdote of the tree from Honduras, mentioned by 

 Humboldt is well known. American trees are yearly de- 

 posited on the coast of Ireland. Wind increases the velo- 

 city of the stream. It is recorded that the Filbury, Eng- 

 lish man of war, was burnt near Jamaica, and that the masts 

 were found near Scotland. The bowsprit of the Little 

 Belt was conveyed nineteen months in a northern direc- 

 tion to the mouth of the B roads. 



Wallace says that in 1682, Esquimaux in leathern canoes 

 came to the Orkney Islands. 



, III. Motion of the tides. The tides are periodical os- 

 cillations of the sea, caused by the sun and moon; but more 

 particularly by the latter. The waters rise highest when 

 the sun and moon are in conjunction and in opposition: the 

 two surfaces being then raised, and producing a more sphe- 

 roidal form even in the equatorial diameter- (Enf. prop. 

 CLXXIV.) The moon's attraction is nearly three times 

 greater than that of the sun- 

 Between the tropics the tides set eastward ; in the north- 

 ern frozen ocean they are weak ; of the antarctic nothing is 

 known. 



r 



^The highest tides are on the coast of France, where they 

 are driven from the English coast, and rise seven or eight 

 fathoms. 



Liiminonsness of the Sea, is more evident at particular 

 times and places. Vespucius was the first modern who no* 

 ticed it. Bacon observed it, and Boyle collected theories 

 to account for it. In 1703 it first attracted attention, and 

 there is a letter, dated that year from Genoa to Paris, stating 

 that the sea had been luminous fourteen nights, which the 

 learned societies in Paris did not believe. 



Four causes have been assigned for it 



1. Absorbed solar light. 3. Electricity. 



2. Marine animals. 4. Decayed animal, and ve- 



getable matter. 





