been originally deposited, were naturally inferred to have been formed in the waters, after the catastrophe had passed away. By such reasonings as these, M. Elie de Beaumont has conceived that he can ascertain the relative ages (according to the vast and loose measurements of age which belong to this subject) of the principal ranges of mountains of the earth's surface. 20. Such estimations of age can, indeed, as we have intimated, be only of the widest and loosest kind; yet they all concur in assigning very great and gigantic periods of time, as having been occupied by the events which have formed the earth's strata, and brought them into their present position. For not only must there have been long ages employed, as we have said, while the successive generations of each group of animals lived, and died, and were entombed in the abraded fragments of the then existing earth; but the other operations which intervened between these apparently more tranquil processes, must also have occupied, it would seem, long ages at each interval. The dislocation, disruption, and contortion of the vast masses of previously existing mountains, by which their framework was broken up, and its ruins covered with beds of its own rubbish, many thousand feet thick, and gradually becoming less coarse and smoother, as the higher beds were deposited upon the lower, could hardly take place, it would seem, except in hundreds and thousands of years. And then again, all these processes of deposition, thus arranging loose masses of material into level beds, must have taken place in the bottom of deep oceans; and the beds of these oceans must have been elevated into the position of mountain ridges which they now occupy, by some mighty operation of nature, which must have been comparatively tranquil, since it has not much disturbed those more level beds; and which, therefore, must have been comparatively long continued. If we accept, as so many eminent geologists have done, this evidence of a vast series of successive periods of alternate violence and repose, we must assign to each such period a duration which cannot but be immense, compared with the periods of time with which we are commonly conversant. In the periods of comparative quiet, such as now exist on the earth's surface, and such as seem to be alone consistent with continued life and successive generation, deposits at the bottom of lakes and seas take place, it would seem, only at the rate of a few feet in a year, or perhaps, in a century. When, therefore, we find strata, bearing evidence of such a mode of deposit, and piled up to the amount of thousands and tens of thousands of feet, we are naturally led to regard them as the production of myriads of years; and to add new myriads, as often as, in the prosecution of geological research, we are brought to new masses of strata of the like kind; and again, to interpolate new periods of the same order, to allow for the transition from one such group to another.