23 POPULAR SCIENCE MONTHLY. 



brought tlie physical geography of that region into its present form. 

 While the presence of man upon the West Indian and eastern Amer- 

 ican plateaus is not even suggested by remains of him, yet at that 

 time there roamed over the savannas and through the forests several 

 animals identical with and many closely related to the existing spe- 

 cies; and this is as near as we may hope to connect the sunken lands 

 with human associations. 



The application of the deep-sea channels to the measurements of 

 the subsidence of the land is a recent innovation. The elevation of 

 mountain regions to great heights has long since passed beyond the 

 liounds of doubt, but their forms have only recently been used for 

 interpreting their history. The reason for this lies in the fact that 

 many of the necessary topogra|)hical and geological explorations 

 have not been made until recent years, and because geologists were 

 chiefly engaged upon problems of greater antiquity than modern land 

 features, especially on fossil remains which told something of the 

 history of the sea basins; so that their interest in these questions 

 caused them to largely overlook the history of the land. 



If we look at the Alpine plateau surmounted by the sublime 

 ^Matterhoru, we may be told by geologists that, somewhere in the 

 Alps, the Tertiary formations have been found at heights of ten or 

 twelve thousand feet; in the Himalaya Mountains similar marine 

 strata occur to an elevation of twenty thousand feet. We are still 

 left in ignorance of the geographical history of the region, in spite 

 of the geological youthfulness of the formations. Since the com- 

 paratively recent Tertiary period much of the molding of the phys- 

 ical features has been effected. If we observe the Matterhorn, as 

 shown in Plate IV, any one may see a gently sloping plain dissected 

 by a valley thousands of feet deep, which has almost passed the 

 canon stage, but is yet very immature. ]Srow the geomorphist or 

 scientific geographer will almost at a glance interpret the story 

 recorded in these forms. The plateau is the remains of a base 

 level of erosion, and bears testimony of its formation at a level 

 of nine thousand or ten thousand feet lower, or near sea level, 

 imd the marine fossils found in the district will tell since what 

 geological epoch the low plains were formed which have since be- 

 come elevated into the high plateau. The Matterhorn itself, in spite 

 of the faults, is largely a remnant of a higher mountain mass, which 

 was worn do"\vai to a base-level floor by the insidious action of the 

 rains and rills. The valley bears record of an elevation so recent, in 

 spite of the hardness of the rocks and the slowness of degradation, 

 that it has not yet entirely passed its youthful stage. The actually 

 •Aoysr excavation of such a great valley, since the last geological period 

 l^receding the modern, certainly impresses us with the enormous 



