on Rivers and Canals. 643 
in Poland; the Don and the Dwina in Ruffia; the 
Amur or Saghalien in Tartary; the Yellow and Blue 
Rivers in China; the rivers of Cambodia, Ava, and 
Ganges, in India ; the Euphrates ; the river Zaire in 
Congo; the Miffiiippi. 
Sixth clafs. The Rhone in France; the Ebro and 
Douro in Spain; the Danube; the Wolga; the Irtifch 
and Oby, the Jenefea and Lena, in Siberia; the river In- 
dus; the Tigris; the Malmiftra in Cilicia. 
Seventh clafs. In this clafs can only be enumerated thofe 
parts of rivers where they defcend from among moun- 
tains into the plain country below; as alfo fome rivers 
palling through the midft of mountains. 
Eighth clafs. To this clafs belong all torrents among 
mountains; fuch, for example, as the Bourns in the 
Highlands of Scotland are delcribed to be. 
SECTION VI. 
A general and eafy method of taking levels through large 
extents of country where rivers pafs ; and alfo of com- 
puting the heights of interior parts of continents above 
the fur face of the fea. 
80. After all I have faid hitherto in this effay, and 
particularly in the foregoing fedtion, what I am about to 
lay 
