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PREFACE. 
The object of the present volume is : to indicate the char¬ 
acter and, approximately, the extent of the changes produced 
by human action in the physical conditions of the globe we 
inhabit; to point out the dangers of imprudence and the neces¬ 
sity of caution in all operations which, on a large scale, inter¬ 
fere with the spontaneous arrangements of the organic or the 
inorganic world ; to suggest the possibility and the importance 
of the restoration of disturbed harmonies and the material im¬ 
provement of waste and exhausted regions ; and, incidentally, 
to illustrate the doctrine, that man is, in both kind and degree, 
a power of a higher order than any of the other forms of ani¬ 
mated life, which, like him, are nourished at the table of 
bounteous nature. 
In the rudest stages of life, man depends upon spontaneous 
animal and vegetable growth for food and clothing, and his 
consumption of such products consequently diminishes the 
numerical abundance of the species which serve his uses. At 
more advanced periods, he protects and propagates certain 
