THE CENTRAL PLAIN. 
39 
present, and he even believes that the rivers drained 
not only the nearer Alpine districts, but the Vorarl- 
berg, the Orisons, North Tyrol to beyond Botzen, 
the Val Tellina, and the north of Italy, even to the 
hake of Lugano and of Maggiore. The Middle Rhine, 
Reuss, Inn, etc., extended considerably further south. 
Several of the smaller streams, such as the Carassina, 
belonging to the Val Blegno, the Forno and Albigno 
and upper waters of the Maira, which now run into 
the Val Bregaglia to Lombardy, still show by their 
direction and their terraces that they originally be- 
longed to the river system of Switzerland. 
“The pebbles of the Nagelflue,” says Bonney, 
“indicate that this river, instead of flowing as the 
Reuss now does for the greater part of its course 
over crystalline rocks, was then engaged in removing 
the overlying sedimentaries, and had only here 
and there cut down into the Granitoid Gneisses and 
Schists.” * 
Glacial Deposits. 
Over the Tertiary strata lie vast masses of glacial 
deposits which increase in thickness as we approach 
the Jura, and cover the whole district with the ex- 
* The Growth and Sculpture of the Alps, Tyndall Lec- 
tures, 1888. 
