THE EARTH. 14' • 



rent being deeper, becomes, of consequence, more fitted for 

 motion. 



With respect to the places from whence rivers proceed, it 

 may be taken for a general rule, that the largest ' and highest 

 mountains supply the greatest and most extensive rivers. I 

 may albO be remarked, in whatever direction the ridge of the 

 mountain runs, the river takes an opposite com'se. If the 

 mountain, for instance, stretches from north to south, the river 

 runs from east to west ; and so contrariwise. These are some 

 of the most generally received opinions with regard to the course 

 of rivers ; however, they are liable to many exceptions ; and no. 

 thing but an actual knowledge of each particular river can lur- 

 nish us with an exact theoiy of its current. 



The largest rivers of Europe are, first, the Wolga, which is 

 about six hundred and fifty leagues in length, extending from 

 Reschow to Astrachan. It is remarkable of this river, that it 

 abounds with water during the summer months of May and 

 June ; but all the rest of the year is so shallow as scarce to 

 cover its bottom, or allow a passage for loaded vessels that trade 

 up its stream. It was up this river that the English attempted 

 to trade into Persia, in which they were so unhappily disap- 

 pointed, in the year 17-11. The next in order is the Danube. 

 The course of this is about four hundred and fifty leagues, from 

 the mountains of Switzerland to the Black Sea. It is so deep 

 between Buda and Belgrade, that the Turks and Christians have 

 fleets of men-of-war upon it ; which frequently engaged during 

 the last war between the Ottomans and the Austrians : however 

 it is unnavigable further down, by reason of its cataracts, which 

 prevent its comrnerce into the Black Sea. The Don, or Tanais, 

 which is four hundred leagues from the source of that branch of 

 It called the Softna, to its mouth in the Euxine Sea. In one 

 part of its course, it approaches near the Wolga ; and Peter the 

 Great had actually begun a canal, by which he intended joining 

 those two rivers ; but this he did not live to finish. The Nieper, 

 or Boristhenes. which rises in the middle of Muscov)', and runs 

 a course of three hundred and fifty leagues, to empty itself into 

 the Black Sea. The Old Cossacks inhabit the banks and islands 

 of this riyer; and frequently cross the Black Sea, to plunder the 



3 Dr HaUey. 



.k3 



