THE EARTH. 



77 



their sails, and the ship's prow seems to di- 

 vide the water ; but, at last, by miserable 

 experience they find, that instead of going 

 forward, they have been all the time reced- 

 ing. The business of currents, therefore, 

 makes a considerable article in navigation; 

 and the direction of (heir stream, and their 

 rapidity has been carefully set down. This 

 some do by the observation of the surface of 

 the current ; or by the driving of the froth 

 along the shore ; or by throwing out what is 

 called the log-line, with a buoy made for 

 that purpose ; and by the direction and mo- 

 tion of this, they judge of the setting, and the 

 rapidity of the current. 



These currents are generally found to be 

 most violent under the equator, where in- 

 deed all the motions of the ocean are most 

 perceivable. Along the coasts of Guinea, if 

 a ship happens to overshoot the mouth of any 

 river it is bound to, the current prevents its 

 return ; so that it is obliged to steer out to 

 sea, and take a very large compass, in order 

 to correct the former mistake. These set in 

 a contrary direction to the general motion of 

 the sea westward ; and that so strongly, that 

 a passage which with the current is made in 

 two days, is with difficulty performed in six 

 weeks against it. However, they do not ex- 

 tend above twenty leagues from the coast : 

 and ships going to the East Indies, take care 

 not to come within the sphere of their action. 

 At Sumatra, the currents, which are extreme- 

 ly rapid, run from south to north ; there are 

 also strong currents between Madagascar 

 and the Cape of Good Hope. On the west- 

 ern coasts of America, the current always 

 runs from the south to the north, where a 

 south wind, continually blowing, most proba- 

 bly occasions this phaenomenon. But the 

 currents that are most remarkable, and those 

 continually flowing, into the Mediterranean 

 sea, both from the ocean by the straits of 

 Gibralter, and at its other extremity, from 

 the Euxine sea by the Archipelago. This 

 is one of the most extraordinary appear- 

 ances in nature, this large sea receiving not 

 only the numerous rivers that fall into it, such 

 as the Nile, the Rhone, and the Po, but also 

 a very great influx from the Euxine sea on 

 one part, and the Ocean on the other. At 

 the same time, it is seen to return none of 



those waters it is thus known to receive : 

 outlets running from it there are none ; no 

 rivers but such as bring it fresh supplies; no 

 straits but what are constantly pouring their 

 waters into it. It has therefore been the 

 wonder of mankind in every age, how and 

 by what means this vast concourse of waters 

 are disposed of; or how this sea, which is 

 always receiving, and never returning, is no 

 way fuller than before. In order to account 

 for this, some have said, that the water was 

 re-conveyed by subterraneous passages into 

 the Red Sea.* There is a story told of an 

 Arabian caliph, who caught a dolphin in this 

 sea, admiring the beauty of which, he let it 

 go again, having previously marked it by a 

 ring of iron. Some time after a dolphin was 

 caught in the Red Sea, and quickly known 

 by the ring to be the same that had been ta- 

 ken in the Mediterranean before. Such, how- 

 ever, as have not been willing to found their 

 opinions upon a story, have attempted to ac- 

 count for the disposal of the waters of the 

 Mediterranean by evaporation. For this 

 purpose they have entered into long calcula- 

 tions upon the extent of its surface, and the 

 quantity of water that would be raised from 

 such a surface in a year. They then com- 

 pute how much water runs in by its rivers 

 and straits in that time ; and find, that the 

 quantity exhausted by evaporation greatly ex- 

 ceeds the quantity supplied by rivers and seas. 

 This solution, no doubt, would be satisfactory, 

 did not the Ocean, and the Euxine, evapo- 

 rate as well as the Mediterranean : and as 

 these are subject to the same drain, it must 

 follow, that all the seas will in this respect 

 be upon a par; and, therefore, there must 

 be some other cause for this unperceived 

 drain, and continual supply. This seems to 

 be satisfactorily enough accounted for by 

 Dr. Smith, who supposes an under current 

 running through the straits of Gibraltar to 

 carry out as much water into the Ocean, as 

 the upper current continually carries in from 

 it. To confirm this, he observes, that nearer 

 home, between the north and south Ireland, 

 the tide is known to run one way at top, and 

 the ebb another way at bottom. This dou- 

 ble current he also confirms by an expen- 



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Kircher Mund. Subt. vol. i. 



