io ALBRECHT PENCE 



Regions of glacial confluence and glacial diffluence are sharply sepa- 

 rated from each other. They have nothing to do with the feeding and 

 melting part of the glacier, and are determined only by the presence 

 or absence of lateral affluents. The confluence and diffluence of 

 glaciers, therefore, may occur as well in its neve region as in its region 

 of ablation, in its feeding, or in its dissipating part (according to H. F. 

 Reid), but generally the confluence prevails in its upper parts and the 

 diffluence in its lower parts. On the north side of the Alps the difflu- 

 ence is excellently represented by the enormous ice fans in the Ger- 

 man Alpen-Vorland, where formerly were the glaciers of the Rhine, 

 the Isar, the Inn, and the Salzach, while in Switzerland the diffluence 

 was hindered by the Jura Mountains so that no regular fans were 

 formed. On the south side, the fan-like diffluence of the ice occurred 

 partly in the Alps, and was really restricted to it in the region of the 

 lakes north of Milan, which we will call Insubrian lakes after the 

 ancient country of the Insubrii, whose capital was Milan. 



Everywhere where a fan-like diffluence of the ice occurred its 

 bed shows ramifications which have a spoke-like arrangement and 

 slope toward their center. Thus, for example, in the fan of the old 

 Rhine glacier. Lake Constance is the center of the fan, its western 

 termination bifurcating into lakes Uberlingen and Zell. In two 

 similar broad furrows, the rivers Schussen and Argen approach the 

 lake from the north and northeast. Lake Constance is the palm 

 of the hand, its western branches and the furrows of Argen and 

 Schussen being fingers which stretch out to the rim of the old glacier. 

 A similar arrangement is found in the fans of the old glaciers of the Inn 

 and the Salzach, the trough of the valleys terminating by branching 

 in the sub- Alpine plains; and every branch is followed by a river 

 flowing toward the Alps, in the direction from which the ice came, 

 thus marking the reversed slope of the bottom of the different branches 

 of the ice which formed the ice-fan. The same features reoccur where 

 the diffluence of the glacier took place in the mountains. Lake Como 

 bifurcates, and the Como branch has no outlet. Its waters must 

 first flow toward the Alps to reach the outlet at Lecco. On the east 

 side of Lake Como a branch of the old Adda glacier penetrated into 

 the Valsassina, whose waters flow toward the Alps in order to reach 

 Lake Como, revealing a reversed slope. A fourth finger of the Adda 



