modern writer
has estimated, that there are in America upwards of four million square
miles of useful soil, each capable of supporting 200 persons; and nearly
six million, each mile capable of supporting 490 persons.[983] If this
conjecture be true, it will follow, as that author observes, that if the
natural resources of America were fully developed, it would afford
sustenance to five times as great a number of inhabitants as the entire
mass of human beings existing at present upon the globe. The new
continent, he thinks, though less than half the size of the old,
contains an equal quantity of useful soil, and much more than an equal
amount of productive power. Be this as it may, we may safely conclude
that the amount of human population now existing constitutes but a small
proportion of that which the globe is capable of supporting, or which it
is destined to sustain at no distant period, by the rapid progress of
society, especially in America, Australia, and certain parts of the old
continent.

_Power of exterminating species no prerogative of man._--But if we
reflect that many millions of square miles of the most fertile land,
occupied originally by a boundless variety of animal and vegetable
forms, have been already brought under the dominion of man, and
compelled, in a great measure, to yield nourishment to him, and to a
limited number of plants and animals which he has caused to increase, we
must at once be convinced, that the annihilation of a multitude of
species has already been effected, and will continue to go on hereafter,
in certain regions, in a still more rapid ratio, as the colonies of
highly civilized nations spread themselves over unoccupied lands.

Yet, if we wield the sword of extermination as we advance, we have no
reason to repine at the havoc committed, nor to fancy, with the Scottish
poet, that "we violate the social union of nature;" or complain, with
the melancholy Jacques, that we

Are mere usurpers, tyrants, and what's worse,
To fright the animals and to kill them up
In their assign'd and native dwelling-place.

We have only to reflect, that in thus obtaining possession of the earth
by conquest, and defending our acquisitions by force, we exercise no
exclusive prerogative. Every species which has spread itself from a
small point over a wide area must, in like manner, have marked its
progress by the diminution or the entire extirpation of some other, and
must maintain its grou