306 THE BEAUTIES OF NATURE CHAP. 
Lake of Constance into the Danube, and so to 
the Black Sea. Then, after the present valley 
was opened between Waldshut and Basle, 
they flowed by Basle and the present Rhine, 
and after joming the Thames, over the plain 
which now forms the German Sea into the 
Arctic Ocean between Scotland and Norway. 
Finally, after the opening of the passage at 
Fort de l’Ecluse, by Geneva, Lyons, and the 
Valley of the Sadne, to the Mediterranean. 
It must not, however, be supposed that 
these changes in river courses are confined to 
the lower districts. Mountain streams have 
also their adventures and vicissitudes, their 
wars and invasions. Take for instance the 
Upper Rhine, of which we have a very inter- 
esting account by Heim. It is formed of 
three main branches, the Vorder Rhine, Hinter 
Rhine, and the Albula. The two latter, after 
meeting near Thusis, unite with the Vorder 
Rhine at Reichenau, and run by Chur, May- 
enfeld, and Sargans into the Lake of Con- 
stance at Rheineck. At some former period, 
however, the drainage of this district was 
very different, as is shown in Fig. 43. 
