6io 



PHYSICAL GEOGRAPHY. 



northerly from the Tip-top house, or at Figs. 79 and 85. But the view 

 from the south-east shows the plateau best, and if it had been taken from 

 a point a little farther east, the feature would show itself more promi 

 nently, as in the last of Oakes s lithographs. The abyss in front is 

 Tuckerman s ravine, with tributary scallopings on the north-west sides. 

 The erosion has been vertical, just as in a gorge worn out of a level 

 plain. It is impossible to descend with safety down the sides of this 

 ravine in most places. And the accessible portions have been rendered 

 less precipitous by the accumulation of loose material, through slides and 

 atmospheric disintegration. Oakes s gulf and Hunting-ton s ravine are 

 other deep gorges excavated out of this plateau. This table-land is less 

 than ten miles in length, and somewhat over 5000 feet in elevation. 



We think, therefore, the proper structure of the Washington group of 

 summits is best expressed by the supposition of a plateau, out of which 



Fig. 78. MTS. ADAMS AND MADISON. 



From near Randolph hill. 



four great ravines have been excavated, and upon which lateral forces 

 have piled up comparatively inferior heaps of contorted rock, constitut 

 ing the presidential summits. With these suggestions in mind, the 

 tourist will easily see the reasons for the special fashioning of every 

 elevation and depression in the Montalban area. 



The modifications induced by stratigraphical structure are perhaps 



