probable extinction, speedily and at no distant period, of hundreds of others,—these families possessed, all of them, of as enduring structures, and of higher types of existence, than those of the older epochs,—and, therefore, upon every fair ground of analogy, are we justified in concluding that there can be no such diversity of ages, under one and the same system of nature, as that of hundreds of thousands of years to the living tribes of earth. When such premises are made the grounds of such inferences, and, again, when the geologist reiterates the statement that these great periods of time correspond wonderfully with the gradual increase of animal life, and the successive creation and extinction of numberless orders of being, and with the incredible quantity of organic remains buried in the crust of the earth, we have just to remind him that betwixt _great_ periods of time, and the _gradual_ increase of animal life, there is no necessary connection. However long and indefinite the time connected with the rocky formations, certain it is that the successive organic tribes were created within a period that admits, and can admit, of no calculation whatever, not even of any analogical illustration from experience or the known laws of nature. The species, however numerous, of every epoch were called at once into being, not gradually but instantly, by the fiat of an all-creative act. Their multiplication and increase depended upon the law of their nature; but how long they were to be privileged to multiply, in one unvarying specific form, according to that law, is a point that comes legitimately within the range of experience and the calculations of existing life. Let not things which differ, therefore, be mixed together. The organic and the inorganic types, in the act of formation, cannot be compared. And no argument can be adduced from the fact of the mere numbers of animal species, or of their individual increase, in support of the assumed length of any geological epoch. Species as well as individuals have perished, and gone out within the narrow limits of our own epoch, and yet have multiplied in progeny through countless myriads.