1878.] 325 [Xiles. 



the deeper valleys to a sufficient height to include an extensive range 

 of meteorological conditions. Such mountains present, upon their 

 slopes, zones of physical climate, which in altitudes are equivalent to 

 the zones of latitudes. Accordingly the atmospheric agencies, which 

 have their part in shaping the mountains, act with different degrees 

 of intensity and with somewhat different results in each of these 

 climatic regions. Upon the culminating portions of these mountains 

 the atmospheric agencies usually predominate, to a greater or less 

 degree, over the other physical forces. But the mechanical powers 

 of the atmosphere diminish as we descend the slopes, and, in their 

 action upon the rocks, usually become subordinate to other denud- 

 ing, agents. Thus the climatic regions of mountains become zones of 

 different geological activities. Such a distribution of geological 

 powers is attended by a corresponding distribution of geological re- 

 sults; therefore, upon such mountain slopes there may occur zones of 

 different physical features. 



Whether or not such physiographic zones are developed upon any 

 mountain slope having a sufficient range of climate, depends in part 

 upon the geological constitution of the mountain. The slopes which 

 furnish the best examples, are those which have a comparatively uni- 

 form geological structure and composition. Different kinds and 

 structures of rock, yielding with different degrees of readiness, ac- 

 quire features winch are more or less independent of altitudes, and 

 which may confuse the characteristics of these zones or obliterate 

 them. It is when similar geological structures are exposed to the 

 predominating physical forces of different altitudes, that these moun- 

 tain zones are best developed. 



The eastern part of the southern slopes of the Bernese Alps pre- 

 sents this combination of geological and meteorological conditions. 

 Having become somewhat familiar with this district, I shall consider 

 the zones of these slopes as types of their kinds, although I am aware- 

 that many other regions might be selected with equal appropriate- 

 ness. Here, as in many other districts, the zones of physical features 

 nearly correspond in position and altitude with the more conspicu- 

 ous regions with which the ordinary tourist has been made familiar. 

 Most of the descriptions we have of the Alps, even those of the 

 most popular character, mention three zones or regions of the moun- 

 tains. The highest of these is the region of "Perpetual Snow-fields 

 and Glaciers," or the "High Alps," below which is the "Alpine 

 Zone," with its elevated pastures called "Alps" and its Alpine vege- 



