CUEEENTS GULE-STEEAM. 101 



these days, with the assistance of steam, a calm is the very 

 time in which most progress is made, and there is no 

 doubt but a time will come when it will be matter of 

 wonder that men could ever have trusted to so uncertain an 

 element as the wind ; yet, if it were not for the winds, 

 currents, and tides, the sea could not maintain its state of 

 purity, for its saltness is not sufficient to prevent the growth 

 of fungi and all sorts of animalculse, which, from their decay, 

 would produce noxious gases and be most injurious to 

 animal life. Its constant motion alone prevents this, and the 

 spores and germs are tossed about until destroyed and 

 eaten up by the inhabitants of the deep who devour every 

 kind of organic matter which is deposited in the sea, 

 and thus it is that the waters of the ocean are so bright 

 and clear that an object can be seen at a considerable 

 depth. 



That the constant currents of the sea prevent the forma- 

 tion and growth of sea- weed, is clearly shown by the great 

 " Sargasso Sea," or tract of weed (Fucus natans), called 

 the Gulf-weed. This great tract embraces thousands of 

 square miles, and is situated in the very middle of the 

 Atlantic Ocean, where there are but few currents ; but 

 surrounding it is the Grulf-Stream, an enormous current 

 of water running at a regular rate of four or five 

 miles an hour. This Grulf-Stream is supposed to be 

 caused by the same laws and influences which determine 

 the trade- winds, namely, a constant rarefaction of the water 

 at the tropical parts of the earth, and a corresponding con- 

 densation at the Arctic portions, for warm water is much 

 lighter than cold, and when the waters of the tropical 

 regions become lighter the heavier waters of the cold 

 regions pressing down more forcibly tend to raise them 

 above their proper level ; they therefore flow towards those 

 very parts which have sunk down by their contraction, and 

 a constant current takes place this current is the Grulf- 

 Stream. It runs from the Grulf of Mexico northwards 

 towards Newfoundland, turning by Iceland towards the 

 British Isles, by France and Spain, onwards to the coasts of 

 Africa and South America, the West Indies, and again to 



