PHYSICAL FEATURES OF THE UNITED STATES 315 



culture were greatly changed. Large tracts denuded of soil were 

 relegated to the growth of timber; others were made hilly by 

 the heaping of drift, and yet others were smoothed by sedimen- 

 tation in the beds of temporary lakes. The new soils have a 

 special quality as compared to those resulting from the decay of 

 rocks, for rock decay involves leaching and the loss of soluble 

 minerals. The ice-mill ground together unleacht samples of 

 many rocks and deposited them with little sorting, so that the 

 glacial soils are often rich in materials which elsewhere need to 

 be artificially supplied. 



The confusion of drainage has yielded results as important in 

 their way as those from the traditionary confusion of tongues at 

 Babel, for the disconcerted streams, having their descent arrested 

 by basins and lakes, are compelled elsewhere to tumble down 

 rapidly, making convenient water powers ; and these water 

 powers have special value because the associated lakes are nat- 

 ural reservoirs, protecting them from flood and drought. As the 

 greater lakes are also natural avenues for commerce, the prov- 

 ince of the Lakes, associating water power with commercial facil- 

 ity, is the natural home of manufacture. 



The physical characters which, after mineral resources and 

 climate, have greatest influence on industrial activities are in- 

 ternal routes for commerce and maritime harbors in their rela- 

 tion to external routes. The lines followed by pioneer settle- 

 ment as well as those to which internal transportation ultimately 

 adjusts itself are greatly influenced by topographic configuration, 

 continuous mountain ranges acting as barriers and low passes 

 through ranges serving as avenues. Long lines of navigable 

 water also have their influence, and for districts whose most 

 practical product is so abundant as to yield a surplus for expor- 

 tation facility of transportation means progress in population 

 and wealth. The consideration of these conditions is attractive, 

 but as they affect various localities unequally their discussion 

 may properly he left for the lecturers who are to speak of more 

 limited districts. 



Harbors, however, though their local quality has local value, 

 are of primary importance to the country as a whole and may 

 be considered today. They are naturally formed in many ways, 

 but only the principal types need be mentioned. Wherever a 

 river reaches the sea the continuous contour of the coast is broken, 

 and there would be a natural harbor but for the opposition of 

 the waves. The outflowing river endeavors to scour a channel 



