THE VALAIS. 
I 15 
ance of a river valley, but is no doubt very ancient, 
probably as old as the Miocene. It belonged 
originally to the Dranse de Bagne, and is most 
likely older than the upper Valais or than the eleva- 
tion of the Bernese range. 
It is indeed difficult to account for the facts, ex- 
cept by assuming that the Dranse was running ap- 
proximately along its present course before the fold- 
ing at St. Maurice commenced, and cut back the 
ridge as it rose. In this case, the Dranse is pro- 
bably an older river than the Rhone, and to it pro- 
perly belongs the valley between Martigny and the 
Lake of Geneva. 
Down to comparatively recent times the lowei 
Valais was marshy, and subject to destructive floods. 
Hence, we find that the towns are generally placed 
on the’ cones of the lateral streams, —Aigle on that 
of La Grande Eau, Bex at the mouth of the Aven- 
con, Monthey of the Viege; Muraz, Vionnaz, Vouvry, 
Aux Evouettes, etc., on the cones of other streams. 
The most remarkable cones are those (i) of the Bois 
Noir (Fig. 107), formed by the torrent of St. Barthe- 
lemy, and above Martigny; (2) that of Chamoson at 
the mouth of the Losenze, which is 4 km. m length, 
and rises from 480 metres to 730 metres, having 
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