Page:Popular Science Monthly Volume 44.djvu/553

From Wikisource
Jump to navigation Jump to search
This page has been proofread, but needs to be validated.
539
THE POSITION OF GEOLOGY.

But although the assumption of the uniformitarians on. the question of degree may be disputed, that on the question of kind admits of no dispute. That rivers excavate and currents distribute the excavated materials, and that the land is mobile and subject to changes of level, no one will contest. The point of contention is the rate at which these operations and changes proceeded formerly as compared with the rate at the present day. The many observations made on the erosive and transporting power of rivers, and on the movements and waste of the land, are admirable in so far as they apply to the silting up of ports, the recession of the coast, and the reclamation of marsh lands; but, though valuable to the engineer, they are misleading to the geologist. They furnish him, it is true, with standards applicable to present changes, and indicate the method in which the erosive power of the rivers and seas has acted in all time, but they give no measure of the amount and rate of work they did at different periods. Nevertheless, knowing what at present is accomplished by their means, it is' reasonable to judge, by ascertaining what their agency accomplished in former days, of the difference in the forces in operation at the several periods. Those forces have to be estimated by the work done in the past, and not by any fixed rate founded upon present work.

Few geologists would, we presume, contest this position; notstanding which, and though many now profess a modified uniformitarianism, the old lines of argument still, with few exceptions, prevail, and the concessions made are more apparent than real, or are of little value. In our opinion, no partial concession can be entertained on the question of degree. It must be an unconditional surrender; for, in contradistinction to method, or manner, where we are on common ground, no common scale on the question of degree is possible in judging of the past by comparison with the present.

As an example of the present position, we may take one argument as presented by the advocates of the uniformitarian school. The observations on the transporting power of the large rivers of the world have shown that the quantity of sediment carried down by them to the sea is, according to one of their estimates, such as would suffice to lower the level of the land about one foot in six thousand years, or about a thousand feet in six million years. Exception might be taken to this estimate in that no account is taken of the calcareous matter removed in solution, which, in fact, is not far from the quantity of insoluble matter carried down mechanically. Let that pass. This measure, or one approximate to it, has been very generally accepted, and is in common use. Hence those geologists, proceeding solely on the assumed postulate, and not attaching due weight to other con-