"/ [Book VIL 



fhall fee but little reafon to doubt of Dr. Halley's hy- 

 pothefis, but may reafonably conclude, that this kind 

 of circulation is carried on through all nature, and that 

 the fea receives back again through the channel of 

 the rivers, that \vater which it parts with to the at- 

 mofphere. 



c All rivers have their foiirce either in mountains, 

 or elevated lakes; and it is in, their defcent from thefe, 

 that they acquire that velocity which maintains their 

 future cunvnt. At firft their courie is generally rapid 

 and headlong ; but it is retarded in its journey by the 

 continual friction againft its banks, by the many ob- 

 fiacles it meets to divert its ftream, and by the plains 

 generally becoming more level as it approaches towards 

 the fea. . 



* Rivers, as every body has feen, arc always broadeft 

 at the rY'Oiith , and grow narrower towards their 

 fource. But what is lefs -known, and probably more 

 delerving curiofity, is, that they run in a more direct 

 channel as they immediately leave their fources j arid 

 that their finuofities and turnings become more nu- 

 merous as they proceed. It is a certain fign among 

 the favages of North America , that they are near the 

 fea, When they find the rivers winding, and every now 

 and then changing their direction. And this is even 

 now become an indication to the Europeans them- 

 felves, in their journies through thofe tracklefs forefts. 

 As thofe finuofities, therefore, increafe as the river ap- 

 proaches the fea, it is noi: to be wondered at, that they 

 fometimes divide, and thus difembogue by different 

 channels. The Danube difembogues into the Euxine 

 by feven mouths j the Nile, by the fame number ; and 

 the Wolga, by feventy. 



1 The largeft rivers of Europe are, firft, the Wolga, 

 which is about fix hundred and fifty leagues in length, 



extending 



