1878.] 327 [Niles. 



ZONE OF GLACIATION. 



When this zone is well developed upon the slopes of the Alps, it 

 extends from near the lower limit of the snow-region downward to the 

 timber-line. The slopes are much more moderate than those above 

 or below, excepting, of course, the steeper sides of the transverse 

 valleys which cross this zone. While there occur here and there pro- 

 jections of rock, which have acquired or retained the rougher features 

 produced by vicissitudes of climate, by far the larger proportion of 

 rock-surfaces show the effects of glacial action in their convexly 

 curved outlines and in the abundance of roches moutonnees. These 

 smoothed surfaces yield much less readily to the atmospheric changes 

 than the rougher surfaces of the region above. There are here, also, 

 accumulations of glacial debris. It is in this zone that the moraines 

 and glacial deposits most frequently retain their original forms, having 

 usually been less changed by aqueous agencies than when they are 

 found in the lower districts. These accumulations present a series 

 of convex outlines, which, although less regular, still harmonize well 

 in general form with the glaciated rock-surfaces. As it is here that 

 the effects of ancient glacial action are best exhibited, and as the 

 principal topographic features have been caused by such action, I 

 call this region the Zone of Glaciation. 



ZONE OF AQUEOUS AGENCIES. 



If we start from the level of the larger Alpine valleys and ascend the 

 range on either side, we usually find the first part of the acclivity 

 steeper than the portion immediately above the timber-line. The 

 slopes of this region are most frequently the sides or walls of the 

 valleys. They are often quite steep and of comparatively uniform 

 grade, and they are frequently clothed with sub-alpine forests, which 

 extend, in but slightly undulating outlines, from the meadows of the 

 valleys to the Alps of the zone above. The symmetrical and graded 

 cones of dejection are frequently conspicuous in this region. In some 

 other valleys, especially in the narrower and lateral ones, precipitous 

 walls of rock predominate, while in many others precipices alternate 

 irregularly with wooded or grassy slopes. Some of the rock-surfaces 

 retain the rounded forms which they had upon the retirement of the 

 ancient glaciers, but upon the sides of the valleys here noticed they 

 are not sufficiently numerous or prominent to be considered the most 

 characteristic features in the topography of the region. Further- 

 more, the weathering power of the atmosphere acts upon these slopes 



