12 Proceedings. 



The reason why the East Lateral Moraine of Ivrea surpasses 

 the West Lateral in height is seen by reference to the map. 

 Many more feeders fall into the Val Baltea from the east than 

 from the west. Detrit^^s carried onto the eastern side of the 

 glacier would finally be discharged on the east, on the plains. 

 The material of Alpine Moraines is more angular than 

 Himalayan detritus, owing to the enormous length of Hima- 

 layan glaciers, some extending thirty miles, so that the 

 detritus is rendered subangular in its long journey. In the 

 Rhone Valley blocks may be found similar to the Himalayan. 



Glaciers are always either advancing or retreating. The 

 Alpine glaciers are now retreating very rapidly ; many of the 

 Himalayan are advancing. The Moraine at Ivrea proves 

 periodic advances and retreats of the glacier. "When the ice 

 began to retreat the Moraine was thrown to the sides ; then 

 came an advance again, and fresh hills of detritus were added. 

 The Eastern Lateral Moraine is four miles across, and shows 

 the lines marking retreat and advance of the glacier. The 

 Western Moraine is not so perfect ; the Eiver Chusella has 

 cut right through it. On the east we find a lower inner 

 Moraine, which was cast up when the glacier was finally 

 retreating. Very beautiful sections may be seen near Arona. 



Opposite every valley the tendency is for a " Fan " to be 

 cast up ; this is caused by the soil brought down by the rivers 

 gradually raising their bed and banks above the level of the 

 surrounding country ; then, in time of flood, a fresh channel 

 is formed, and the same process is repeated. 



Some rounded hills are not Moraines, but are bosses of 

 diorite, over which the ice has travelled, as the stria-marks 

 upon them prove. We have also near Ivi'ea clear proof that 

 ice can excavate hollows out of harder rock on a smaU scale, 

 leaving beautiful little lakes. Larger lakes, such as Como 

 and Maggiore, do not owe their origin to ice-excavation, but 

 are to be accounted for by yet older configuration of the sur- 

 face ; mountain-tarns are often formed by ice-action. That 

 a large lake extended in recent times almost up to Ivrea is 

 proved by beds of clay containing fresh-water shells. The 

 largest lake left, the Lago d'lvroni, has no outlet ; the Dora 



