RELATIONS TO OTHER SCIENCES 621 



Further, the new land, almost as soon as it has appeared above the 

 waters, begins to be sculptured by the exogene processes. These 

 processes may, in the one case, be hindered by reason of the rapidly 

 extending cover of vegetation; on the other hand, they may be able 

 to work for a long time undisturbed by any hindrance. In general, 

 the exogene processes require a much greater interval of time to 

 subdue a land surface than do the plants in order to cover it with a 

 dense cloak of vegetation. The Kerguelen still show the surface 

 relief imposed upon them by their glaciation, and running water has 

 not yet been able to remodel them. The Alps, which furnish us with 

 a splendid example of the adjustment of vegetational covering to the 

 zones of elevation, still betray in all their features the glaciation to 

 which they were subjected during the glacial period. Thus we find 

 that the morphologic adjustment of a country to its structure and 

 its climate, which indicates that it has reached the mature stage 

 of the geographic cycle, succeeds to the physiogeographical stage of 

 maturity by a very considerable interval of time, and in order to 

 produce a complete physiographic correlation between the two, it 

 requires an amount of time which must be measured by geologic 

 units. This correlation, however, will not be reached in the same 

 way under all conditions. In many cases aqueous erosion works so 

 vigorously that it destroys an existing dense covering of plants, 

 producing ravines and gorges which remain almost barren of vegeta- 

 tion because of their steep walls, and must give, even to a non- 

 geographical observer, the impression of a disturbing attack upon 

 an otherwise harmonious set of conditions. 



Simple as physiogeographic correlation is, in its systematic 

 relationships, yet it leads to an extraordinarily large number of 

 individual cases which call for regional consideration. It forms 

 the chief approach to the physical science of the land. The latter, 

 for its part, cannot leave out of consideration the human element, 

 since Man revolutionizes the plant covering of the land, controls 

 the rivers, and influences the relief of the land by means of his roads 

 and settlements. Thus regional physiogeography is closely related 

 to biogeography. 



The total natural features of any region we have seen to depend, 

 not only upon its own peculiarities and absolute position, but also 

 to a controlling degree upon its position with relation to other land 

 areas. Fundamental changes in any land make themselves felt far 

 beyond its boundaries. If a lowland along the boundaries of a con- 

 tinent become submerged below the sea, as may result from a very 

 slight crustal movement, then the influence of the oceanic climate 

 reaches much farther inland. This is excellently shown by the cli- 

 matic advantages which Europe draws from the presence of the 

 North Sea and the Baltic. Alterations in the lands disturb the physio- 



