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AN ESSAY ON THE
man who considers the subject deeply can well doubt.
Many reasons occur why this oscillation has been less obvious, and less decidedly confirmed by experience, than might naturally be expected.
One principal reason is, that the histories of mankind that we possess, are histories only of the higher classes. We have but few accounts that can be depended upon of the manners and customs of that part of mankind, where these retrograde and progressive movements chiefly take place. A satisfactory history of this kind, of one people, and of one period, would require the constant and minute attention of an observing mind during a long life. Some of the objects of enquiry would be, in what proportion to the number of adults was
the
