PREFACE. 
V 
space required for the convenience of man, and often, by the 
drifting of their particles, overwhelm the fields of human indus¬ 
try with invasions as disastrous as the incursions of the ocean. 
On the other hand, on many coasts, sand hills both protect 
the shores from erosion by the waves and currents, and shelter 
valuable grounds from blasting sea winds. Man, therefore, 
must sometimes resist, sometimes promote, the formation and 
growth of dunes, and subject the barren and flying sands to 
the same obedience to his will to wdiich he has reduced other 
forms of terrestrial surface. 
Besides these old and comparatively familiar methods of 
material improvement, modern ambition aspires to yet grander 
achievements in the conquest of physical nature, and projects 
are meditated which quite eclipse the boldest enterprises hith¬ 
erto undertaken for the modification of geographical surface. 
The natural character of the various fields where human 
industry has effected revolutions so important, and where the 
multiplying population and the impoverished resources of the 
globe demand new triumphs of mind over matter, suggests a 
corresponding division of the general subject, and I have con¬ 
formed the distribution of the several topics to the chronologi¬ 
cal succession in w r hich man must be supposed to have ex¬ 
tended his sway over the different provinces of his material 
kingdom. I have, then, in the Introductory chapter, stated, 
in a comprehensive way, the general effects and the prospec¬ 
tive consequences of human action upon the earth’s surface 
and the life which peoples it. This chapter is followed by 
four others in which I have traced the history of man’s indus- 
