THE CENTRAL PLAIN. 
37 
mountains. These deposits, forming the Nagelflue, 
consist of coarse agglomerates and gravels. 
The pebbles of the Nagelflue are often more 
or less flat, and such pebbles are frequently ar- 
ranged somewhat like the tiles of a roof, so as best 
to stand the current. They therefore indicate the 
direction of the streams, showing them in general to 
have run from S.E. to N.W. They are larger near 
the Alps, as for instance at the Rigi and the Napf; 
and get gradually smaller to the north. Exceptions 
may no doubt be found, and along the Rhine the 
gravels contain some large blocks and pebbles of 
Jurassic limestone. These, however, belong to the 
Black Forest, and have come from the north. 
Dr. Frlih* has made a careful examination of the 
pebbles forming the Nagelflue. Many come from the 
neighbouring Flysch. Of many the origin cannot be 
determined. Pebbles, for instance, from the Flysch 
and the Idas are in many cases indistinguishable, 
unless indeed they contain fossils. These are un- 
fortunately very rare. Neither Rutimeyer nor Fruh, 
in spite of most careful search, have found any 
fossils in the great mass of Nagelflue forming the 
Rigi. 
Heim, however, has met with fragments of Triassic 
* Neue Denkschrif telly 1890. 
