70 F. P GULLIVER — PLANATION AND DISSECTION OF URAL MOUNTAINS 



and in various valleys and on grades of former river-courses,wbile sketches 

 and profiles were made from these and many other points. Within the 

 short limits of a month, however, only a very small area could be visited, 

 even with the phenomenal facilities for travel in an undeveloped region 

 given so freely by the Czar of Russia and all those who carried out his 

 wishes ; therefore the work done upon the dissection of this mountain 

 region on the borders of Europe and Asia, and in the midst of a vast em- 

 pire, can only be considered as a reconnaissance — a first attempt to solve 

 the problem of the physiographic development of the Ural mountains. 



In putting together, several months after the trip was made, the results 

 obtained in various localities, there seems to be such an accordance in the 

 general history of stream development that the writer is inclined to put 

 forward rather strongl}^ his impression in regard to the stages of stream 

 dissection, gathered from two trips taken across the central portions of 

 these mountains, and to offer it as a working hypothesis for future study 

 of the development of the Urals. 



Plan of Paper 



The Russian work is first considered, and then the general features of 

 the Urals are described — the planed uplands, the ridges rising to nearly 

 the same elevations, the gentle arch formed by these summits, the sum- 

 mit-level plane descending gradually to the west until it merges into the 

 upland levels of the great plain of central Russia. The upland level of 

 Urals is shown to have in several places a leather steep fall-off to the Sibe- 

 rian plain, though in other places the plane of the summits merges into 

 that of the great Tertiary deposits of northwestern Asia. The quartzite 

 peaks and the other masses of more resistant rock which rise above the 

 general summit level are described, and a general discussion is given of 

 the valleys cut beneath the main planed surface of the Urals. 



Planation in general is next taken up, and a distinction is sought be- 

 tween planed surfaces formed in four ways : First, those formed b}'^ rivers 

 wearing down the land to baselevel ; second, those produced by the attack 

 of the sea on a stationary land-mass ; third, those abrasion surfaces 

 resulting from sea attack on a slowl}'^ sinking land-mass; fourth, those 

 approximations to a uniform level due to more rapid wearing of higher 

 summits. 



Various parts of the Urals are then considered in detail, and the stages 

 of dissection seen in each are compared and contrasted with one another. 

 The grade-plains seen in various localities accord so well in relative 

 breadth and elevation that the conclusion of the paper is that the most 

 probable history of the dissection of the Ural mountains consists of three 



