THE PRAIRIES. 

 By W .1 McGf.k. 



When first explored by white men the eastern United States was 

 wooded j much of the interior was woodless — the "prairie" of the French 

 explorers, whose designation promises to outlive the condition described 

 by the term; still farther westward lay the Great Plains, with which 

 the prairies merged, and beyond lay the mountains. During this day's 

 journey the route traverses a representative prairie land — the iden- 

 tical tract to which the name was originally applied. Now it is diver- 

 sified, sometimes by natural groves or belts of woodland along the 

 rivers, sprang up since the day of aboriginal prairie fires ended; else- 

 where by artificial groves, hedges, and wind-breaks, such as abound 

 over most of the interior region. 



The prairie soil is commonly the long-weathered surface of one of 

 the two great glacial drift sheets, antedating the terminal moraine. 

 Generally the drift grades upward into a loam, sometimes loess-like, 

 but more commonly displaying the characters of clay. Near the Mis- 

 sissippi, however, this loam deposit has developed into a fairly well- 

 defined loess, which is not, however, so distinctive or so abundantly 

 developed as on the Missouri. In the interior the loam is commonly 

 so thin that drift boulders may be seen approaching the soil in the 

 railway cuts, and not infrequently they lie scattered over the surface 

 in considerable numbers. All, or nearly all, of these boulders are far- 

 traveled erratics, carried down from near or beyond the northern bound- 

 ary of the United States. 



The relief is low, the surface undulating gently; the configuration is 

 the product of faint hydrodynamic sculpture, for the most part directed 

 by the antecedent glacial configuration and by the temporary water- 

 ways born of the melting ice. It is noteworthy that this surface, 

 primarily ice fashioned, is now so far modified by waterwork that 

 practically the entire surface is well drained. Marshes occur only 

 rarely and lakes never. In this respect the extra-niorainal surface is 

 strongly distinguished from the intra-niorainal area, in which lakes 

 abound and marshes are innumerable. 



449 



451 ge 29 



