1Y 
PREFACE. 
esculent vegetables and certain fowls and quadrupeds, and, at 
the same time, wars upon rival organisms which prey upon 
these objects of his care or obstruct the increase of their num¬ 
bers. Hence the action of man upon the organic world tends 
to sub, ert the original balance of its species, and while it reduces 
the numbers of some Of them, or even extiipates them. 
gether, it multiplies other forms of animal and vegetable life. 
The extension of agricultural and pastoral industry involves 
an enlargement of the sphere of man’s domain, by encroach¬ 
ment upon the forests which once covered the greater part of the 
earth’s surface otherwise adapted to his occupation. The fell¬ 
ing of the woods has been attended with momentous conse¬ 
quences to the drainage of the soil, to the external configura¬ 
tion of its surface, and probably, also, to local climate; and 
the importance of human life as a transforming power is, per¬ 
haps, more clearly demonstrable in the influence man has thus 
exerted upon superficial geography than in any other result of 
his material effort. 
Lands won from the woods must be both drained and irri- 
. 
gated; river banks and maritime coasts must be secured by 
means of artificial bulwarks against inundation by inland and 
by ocean floods; and the needs of commerce require the im¬ 
provement of natural, and the construction of artificial chan¬ 
nels of navigation. Thus man is compelled to extend over the 
unstable waters the empire he had already founded upon the 
solid land. 
The upheaval of the bed of seas and the movements of 
water and of wind expose vast deposits of sand, which occupy 
