HISTORY OF 



the ocean on one part pours into the ocean on the 

 other. In this manner, therefore, is the sea car- 

 ried with an unceasing circulation round the 

 globe ; and at the same time that its waters are 

 pushed back and forward with the tide, they 

 have thus a progressive current to the west, 

 which, though less observable, is not the less real. 

 Besides these two general motions of the sea, 

 there are others which are particular to many 

 parts of it, and are called currents. These are 

 found to run in all directions, east, west, north, 

 and south ; being formed, as was said above, by 

 various causes ; the prominence of the shores, 

 the narrowness of the straits, the variations of 

 the wind, and the inequalities at the bottom. 

 These, though no great object to the philoso- 

 pher, as their causes are generally local and ob- 

 vious, are nevertheless of the most material con- 

 sequence to the mariner ; and without a know- 

 ledge of which he could never succeed. It 

 often has happened, that when a ship has un- 

 knowingly got into one of these, every thing 

 seems to go forward with success, the mariners 

 suppose themselves every hour approaching their 

 wished-for port, the wind fills their sails, and the 

 ship's prow seems to divide the water ; but, at 

 last, by miserable experience they find, that in- 

 stead of going forward, they have been all the 

 time receding. The business of currents, there- 

 fore, makes a considerable article in navigation ; 

 and the direction of their stream, and their rapi- 

 dity, has been carefully set down. This some do 

 by the observation of the surface of the current ; 



56 



