nd Norway. Finally, after the opening of the
passage at Fort de l'Ecluse, by Geneva, Lyons, and the Valley of the
Saone, 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 interesting 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, Mayenfeld, and Sargans into
the Lake of Constance at Rheineck. At some former period, however, the
drainage of this district was very different, as is shown in Fig. 43.

The Vorder and Hinter Rhine united then (Fig. 43) as they do now at
Reichenau, but at a much higher level, and ran to Mayenfeld, not by
Chur, but by the Kunckel Pass to Sargans, and so on, not to the Lake of
Constance, but to that of Zurich. The Landwasser at that time rose in
the Schlappina Joch, and after receiving as tributaries the Vereina and
the Sardasca, joined the Albula, as it does now at Tiefenkasten; but
instead of going round to meet the Hinter Rhine near Thusis, the two
together travelled parallel with, but at some distance from, the Hinter
Rhine, by Heide to Chur, and so to Mayenfeld.

In the meanwhile, however, the Landquart was stealthily creeping up the
valley, attacked the ridge which then united the Casanna and the
Madrishorn, and gradually forcing the passage, invaded (Fig. 44) the
valleys of the Schlappina, Vereina, and Sardasca, absorbed them as
tributaries, and, detaching them from their allegiance to the
Landwasser, annexed the whole of the upper province which had formerly
belonged to that river.

[Illustration: Fig. 43.--River system round Chur, as it used to be.]

The Schyn also gradually worked its way upwards from Thusis till it
succeeded in sapping the Albula, and carried it down the valley to join
the Vorder Rhine near Thusis. In what is now the main valley of the
Rhine above Chur another stream ate its way back, and eventually tapped
the main river at Reichenau, thus diverting it from the Kunckel, and
carrying it round by Chur.

[Illustration: Fig. 44.--River system round Chur, as it is.]

At Sargans a somewhat similar process was repeated, with the addition
that the material brought down by the Weisstannen, or p