Geographic Methods in Geologic Investigation. 19 



inner valleys of the Himalaya. When thus studied, the endless 

 variety of the topography will be considered in its proper 

 relations, and it will not seem as hopeless as it does now to 

 gain a rational understanding and appreciation of geographic 

 morphology. 



We should first recognize the fact that a geographic individual 

 is an area, large or small, whose surface form depends on a single 

 structure. Boundaries may be vague, different individuals may 

 be blended or even superposed, but in spite of the indefiniteness, 

 the attempt to sub-divide a region into the individuals that com- 

 pose it will be found very profitable. In a large way the Apj)a- 

 lachian plateau is an individual ; the Adirondacks, the terminal 

 moraine of the second glacial epoch are others. In a small way, 

 a drumlin, a fan delta, a mesa, are individuals. The linear 

 plateaus of middle Pennsylvania are hybrids between the well- 

 developed linear ridges of the mountains farther east and the 

 irregular plateau masses farther west. 



A rough classification of geographic individuals would group 

 them under such headings as plains, plateaus, and rough broken 

 countries of horizontal structure ; mountains of broken, tilted or 

 folded structure, generally having a distinct linear extension ; 

 volcanoes, including all the parts from the bottom of the stem or 

 neck, up to the lateral subterranean expansions known as lacco- 

 lites, and to the surface cones and flows ; glacial drift ; wind 

 drift. The agents which accomplished the work of denudation 

 are also susceptible of classification : rivers according to the ar- 

 rangement of their branches, and their imperfections in the form 

 of lakes and glaciers. The valleys that rivers determine may be 

 considered as the converse of the lands in which they are cut ; 

 and the waste of the land on the way to the sea is susceptible of 

 careful discrimination : local soil, talus, alluvial deposits, fan 

 cones and fan deltas, flood plains and shore deltas. Their varia- 

 tions dependent on climatic conditions are of especial importance. 

 The structures formed along shore lines are also significant. This 

 list is intentionally brief, and the lines between its divisions are 

 not sharply drawn. It undoubtedly requires discussion and criti- 

 cism before adoption. It differs but slightly from the common 

 geographic stock in trade, but for its proper application it requires 

 that the geographer should be in some degree a geologist. 



The changes in any geographic individual from the time when 

 it was offered to th e destructive forces to the end of its life, when 



