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 with the plants and animals thus commemorated. According to geological evidence, the race of man is a novelty upon the earth;--something which has succeeded to all the great geological changes.
16. And in this, almost all geologists are agreed. Even those who hold that, in other ways, the course of change has been uniform;--that even the introduction of man, as a new species of animal, is only an event of the same kind as myriads of like events which have occurred in the history of the earth;--still allow that the introduction of man, as a moral being, is an event entirely different from any which had taken place before; and that event is, geologically speaking, recent. The changes of which we have spoken, as studied by the geologist in connection with the works of man, the destruction of buildings on sea-coasts by the incursions of the ocean, the removal of the shore many miles away from ancient harbors, the overwhelming of cities by earthquakes or volcanic eruptions; however great when compared with the changes which take place in one or two generations; are minute and infinitesimal, when put in comparison with the changes by which ranges of mountains and continents have been brought into being, one after another, each of them filled with the remains of different organic creations.