316 LECTURE XI. 



in other places formed temporary lakes. This retreat of tlie 

 glaciers was manifestly a very complicated plienomenon, as the 

 main features of the formation of the soil^ as they exist at 

 present, were already extant (by which assertion we deny what 

 has recently been asserted, namely, that the glaciers at the 

 period of their greatest extent scooped out, in the soft molasse 

 soil, valleys and lake basins) . The glaciers remained longer 

 in the valleys and the basins, and sent forth branches between 

 the molasse hills already free from ice. It must further be 

 taken into consideration that such a retreat was never uniform. 

 The alternation of colder or warmer years, and consequent 

 variations of the hmits of glaciers and of their elevation are 

 common phenomena, and the history of our Alps speaks of 

 meadows and fields, alternately covered with or free from 

 glaciers. Many accui'ate local investigations are requisite 

 before we shall possess a full account of the retreat of the 

 glaciers in Switzerland, though we have a general notion of its 

 main features. 



The retreat of the glaciers is evident at some distance from 

 the Alps, in the great valleys and lake basins, where the ice 

 continued as such for a longer period. In the immediate 

 vicinity of the lakes of Geneva, Sempach, Ziirich, Hallwyl, 

 Greifen, and Pfafiikon, in the valleys of the Aar near Berne, of 

 the Reuss near Bremgarten, of the Limmath near Baden, may 

 be seen terminal morains, which testify to the preservation of 

 the glaciers in the lake basins and deeper valleys. 



Morlot very justly observes, that this persistence of the ice 

 must have continued for a considerable time, as some of these 

 moraines are of immense size. But this preservation must 

 have been attended with same phenomena which accompany 

 the retreat of glaciers. Glaciers which stretch forth their icy 

 tongues through the basin of the lake of Geneva, up to Geneva 

 a.nd Nyon, which penetrated the Eeuss valley up to Mellingen, 

 the Limmath valley up to Baden, and probably filled up the 

 basin of the lake of Constance, must necessarily have produced 

 larger masses of water than the present dwarfs, which cannot 

 transgress the limits of the inner Alps. The same alluvial 

 formation was deposited in front and on the sides of these 



