The atmosphere gradually freed itself from its weight of water-vapor, the rains descended, and the ocean took form and contour. We are concerned only with the outlines of Geology, not with its details. It is full of the most interesting facts, but is foreign to our present purpose. We will only say, there is a marked progression in the scale and importance of life forms. The lower forms of animals appear first to be followed in time by the higher. It is true that some forms have survived through all the changes of Geological time to the present: yet, speaking generally, some forms of life are peculiar to each age, and the general phase of animal life is different with each period. They thus form epochs in the history of the world as read from the rocks, and though the beginning and ending of each age may blend by insensible gradations with that of the preceding and following, yet, taken as a whole, we observe in each such singularities of form and structure as to give name to each particular age. In the fullness of time man appears; and it is our pleasant task to trace the evidence of his primitive state, his growth in culture, and his advancement made before the dawn of history. Our inquiry, then, is as to his prehistoric state. We use this term in the same sense as Dr. Wilson uses it: that is, to express the whole period disclosed to us by means of archæological evidence, as distinguished from what is known through historical records. We can not doubt but that this includes by far the largest portion of man’s existence. The time embraced within historical records, though different in different portions of the world, is but a brief period in comparison to the duration of time since he first went forth to possess the Earth. If we can make plain to our readers that man has lived in the world an extremely long time, going back indeed to a former Geological age—that his first state was very low and rude—that he has risen to his present high estate by means of his own exertions continued through long ages—and from this form a prophecy of a golden age to come in the yet distant future, we shall feel that we have not written in vain. The Sphinx [1] Von Hellwald: “Smithsonian Report,” 1866. [2] Palgrave, [3] Lubbock: “Prehistoric Times,” p. 2. Chapter II EARLY GEOLOGICAL PERIODS.1