Half a century ago George P. Marsh wrote: 



Nature has provided against the absolute destruction of any of her 

 elementary matter, the raw material of her works * * * but she 

 has left it within the power of man irreparably to derange the combina- 

 tions of inorganic matter and organic life, which through the night of 

 aeons she had been proportioning and balancing to prepare the earth for 

 his habitation * * * 10 



To what extent have we in the United States "deranged 

 the combinations" of physical, chemical, and biologic 

 factors referred to by Marsh ? This question sets the theme 

 of the next section. 



10 Man and Nature; or Physical Geography as Modified by Human Action, New York, 

 1864, p. 35. 



18 



