13. But the existence of man upon the earth being thus an event of an order quite different from any previous part of the earth's history, the question occurs, how long has this state of things endured? What period has elapsed since this creature, with these high powers and faculties, was placed upon the earth? How far must we go backward in time, to find the beginning of his wonderful history?--so utterly wonderful compared with anything which had previously occurred. For as to that point, we cannot feel any doubt. The wildest imagination cannot suggest that corals and madrepores, oysters and sepias, fishes and lizards, may have been rational and moral creatures; nor even those creatures which come nearer to human organization; megatheriums and mastodons, extinct deer and elephants. Undoubtedly the earth, till the existence of man, was a world of mere brute creatures. How long then has it been otherwise? How long has it been the habitation of a rational, reflective, progressive race? Can we by any evidence, geological or other, approximate to the beginning of the Human History? 14. This is a large and curious question, and one on which a precise answer may not be within our reach. But an answer not precise, an approximation, as we have suggested, may suffice for our purpose. If we can determine, in some measure, the order and scale of the period during which man has occupied the earth, the determination may serve to support the analogy which we wish to establish. 15. The geological evidence with regard to the existence of man is altogether negative. Previous to the deposits and changes which we can trace as belonging obviously to the present state of the earth's surface, and the operation of causes now existing, there is no vestige of the existence of man, or of his works. As was long ago observed,[3] we do not find, among the shells and bones which are so abundant in the older strata, any weapons, medals, implements, structures, which speak to us of the hand of man, the workman. If we look forwards ten or twenty thousand years, and suppose the existing works of man to have been, by that time, ruined and covered up by masses of rubbish, inundations, morasses, lava-streams, earthquakes; still, when the future inhabitant of the earth digs into and explores these coverings, he will discover innumerable monuments that man existed so long ago. The materials of many of his works, and the traces of his own mind, which he stamps upon them, are as indestructible as the shells and bones which give language to the oldest work. Indeed, in many cases the oldest fossil remains are the results of objects of seemingly the most frail and perishable material;--of the most delicate and tender animal and vegetable tissues and filaments. That no such remains of textures and forms, moulded by the hand of man, are anywhere found among these, must be accepted as indisputable evidence that man did not exist, so as to be contemporary