1887.] Professor Sacco on Origin of Great Alpine Lakes. 271 
Monday , 20 th June 1887. 
Sheriff FORBES-IPtVINE, Vice-President, in the Chair. 
The following Communications were read : — 
Among the many and various controversies to which the geo- 
logical study of the great chain of the Alps has given rise, not the 
least interesting is that which has reference to the origin of the 
beautiful lakes which occur most numerously in the lower reaches 
seems to me to explain the origin of these remarkable basins, and 
in place of these I now venture to adduce one of my own, which 
has been suggested by some years’ observations on the Tertiary and 
Quaternary accumulations of the valley of the Po. Of course, it 
will be understood that I am far from denying that lacustrine 
basins may owe their origin to many various causes ; and for lakes 
in general I am inclined to adopt some such classification as the 
following : — 
It is not, however, with lakes in general that I am now about to 
deal, but with our Alpine lakes in particular. In commencing the 
1. On the Origin of the Great Alpine Lakes. By Professor 
Federico Sacco, University of Turin. 
of the mountain valleys. None of the theories hitherto set forth 
Flexures of strata. 
Fractures. 
Superficial inequalities of deposits. 
^Crateral hollows. 
f Morainic accumulations. 
Ice. 
Alluvial deposits. 
Dunes. 
Lake-basins formed by dams I Littoral banks of sand, &c. 
or barriers, as by . . . ' Landslips and rock-falls. 
Drift-wood. 
Lava. 
Coral reefs. 
. Beaver dams. 
Lake-basinsformedby erosion, 
as by 
f Water, both as a subaerial and subterranean 
| agent, causing local subsidences by removal 
■{ of materials in solution, &c. 
| Ice. 
I Wind. 
VOL. XIV. 
3/11/87 
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