146 
SCENERY OF SWITZERLAND. 
spread as it were in a fan, and that those from one 
district do not overlap those from another, as would 
be the case if they had been distributed by rivers or 
icebergs: for instance, those of the West Jura come 
from Mont Blanc and from the Valais, those of the 
Bernese Jura from the Bernese Oberland, and those 
of Argovie from the eastern cantons and the Rhine.* 
Not only are the blocks from each drainage area 
kept separate, but even, as a rule, those from the two 
sides of the same valley. I say as a rule, because 
in some few cases the glaciers appear to have varied 
in relative dimensions, one encroaching for a time on 
another, and in its turn being driven back. This 
however only applies to some few exceptional areas, 
as for instance between the glaciers of the Linth and 
the Reuss. 
Again, the erratic blocks are specially numerous 
on the summits and slopes of hills, much more than 
in valleys: they are not sorted in sizes, but even the 
largest are found perhaps 50, or even 100, miles 
from their original site. The smaller blocks are 
often polished and striated, like those on existing 
glaciers. 
For these and other reasons there can be no 
Agassiz, Etudes sur les Glaciers . 
