ir.8 A HISTORY OF 



of waters are disposed of; or how this sea, which is always rer.en ing, 

 and never returning, is no way fuller than before. In order to ac- 

 count for this, some have said, that the water was reconveyed by sub- 

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

 Arabian califf, 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 taken in tho 

 Mediterranean before. Such, however, as have not been willing to 

 found their opinions upon a story, have attempted to account for the 

 disposal of the waters of the Mediterranean by evaporation. For this 

 purpose they have entered into long calculations upon the extent of 

 its surface, and the quantity of water that would be raised from such 

 a surface in a year. They then compute how much water runs in by 

 its rivers and straits in that time ; and find, that the quantity exhaust- 

 ed by evaporation, greatly exceeds the quantity supplied by rivers 

 and seas. This solution, no doubt, would be satisfactory, did not the 

 ocean, and the Euxine, evaporate as well as the Mediterranean : and as 

 t'-ese are subject to the same drain, it must follow, that all the seas 

 >ill 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 Gibral- 

 tar 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 the south foreland, the tide is 

 known to run one way at top, and the ebb another way at bottom. 

 This double current he also confirms by an experiment communicated 

 to him by an able seaman, who being with one of the king's frigates 

 in the Baltic, found he went with his boat into the mid-stream, and was 

 carried violently by the current ; upon which a basket was sunk, with 

 a large cannon-ball, to a certain depth of water, which gave a check 

 to the boat's motion ; as the basket sunk still lower, the boat was 

 driven, by the force of the water below, against the upper current ; 

 and the lower the basket is let Jjwn, the stronger the under current 

 was found, aaj .he quicker was the boat's motion against the upper 

 stream, which seemed not to be above four fathom deep. From hence 

 we readily infer, that the same cause may operate at the straits of Gib- 

 raltar ; and that while the Mediterranean seems replenishing at top, 

 it may be emptying at bottom. 



The number of the currents at sea are impossible to be recounted, 

 nor indeed are they always known ; new ones are daily produced by 

 a variety of causes, and as quickly disappear. When a regular cur 

 rent is opposed by another in a narrow strait, or where the bottom of 

 the sea is very uneven, a whirlpool is often formed. These were 

 formerly considered as the most formidable obstructions to naviga- 

 tion ; and the ancient poets and historians speak of them with terror ; 

 chey are described as swallowing up ships, and dashing them against 

 ihe rocks at the bottom : apprehension did not fail to add imaginary 



* Ki-cl.cr Mundt. Subt. voL L 



