Davis — Bearing of Physiography tipo?i /Suess' Theories. 269 



opinion, be adduced as an example of "tangential movement 

 directed toward the south " (Suess, Das Antilitz der Erde, i, 

 603 ; French translation, i, 619), nor should its topographic 

 arrangement be taken to support the thesis that a certain curva- 

 ture of ranges and a certain disposition of steeper slopes, noted 

 in various mountain systems and described for the Tian Shan 

 by Mushketof, are either the result of or the index of tangen- 

 tial pressure. The Tian Shan appears to be the result of dis- 

 placements that have taken place in part of a very extensive 

 degraded region : as a consequence of the displacements, large 

 areas, that were previously below the reach of effective attack 

 by streams, have come to be high above baselevel, so that they 

 are exposed to the most energetic erosion. Having lived 

 nearly through one cycle, they have now entered a second cycle 

 of mountain sculpture ; but there is no clear reason for thinking 

 that forces of compression rather than forces of uplift have 

 acted to renew their mountain height. 



The case of the Tian Shan is less exceptional than it may 

 appear at first sight. It is now nearly thirty years since Gilbert 

 announced that forces of uplift, perhaps involving horizontal 

 extension, and not forces of horizontal compression, gave the 

 best explanation of the Basin ranges of Utah and Nevada. At a 

 later date, various other ranges in the United States came to be 

 regarded as uplifted masses, with more or less warping or tilting, 

 but without recognizable compression, because their even crest 

 lines or highlands appeared to be the result of peneplanation 

 in an earlier cycle of erosion : the Sierra Nevada in California 

 and the Appalachians in the Atlantic States were among the 

 first to be thus explained ; since then, the Cascade and the Coast 

 ranges of Oregon and Washington have been similarly treated, 

 and Gilbert has lately given an account of a lofty and dissected 

 peneplain in the mountains of Alaska. In the meantime, simi- 

 lar results have been reached in Europe. The highland f jelds 

 of Norway are now treated by Reusch and others as having 

 been reduced to moderate relief by long-continued erosion 

 during a lower stand of the land, and afterwards given a greater 

 elevation: there is no indication that their present altitude 

 has been gained by crustal compression. More recently, de 

 Martonne has announced a similar sequence of events for the 

 Carpathians, and Penck has done the same for the Alps. 

 Willis' recent explorations in China led him to similar results 

 regarding extensive mountainous tracks in that far-off country. 

 It was indeed a matter of special interest to the physiographers 

 who attended the International Geographic Congress last autumn 

 to hear the independent testimony of these three observers to 

 the effect that the ranges which they described did not owe 

 their present altitude to forces of compression, however much 



