—a term, in our humble opinion, much more probable than the other.
On another point our two allies (allies in the sense of working at the same subject) are in irreconcilable antagonism. The physicists tell us that uniformity of action in all time is impossible, while the uniformitarians say that such a shortening of geological time as would follow on the acceptance of the physical argument is against all geological experience. Not only do these opinions clash, but those also concerning the rigidity of the earth and the thickness of its crust are widely divergent. None of these contentions can, however, be disregarded, for we must all recognize the importance of considering the question from every point of view. The argument in favor of uniformity of action has been put before us with so much skill and ability, and possessing as it does the charm of an infallible faith, that uniformitarianism has become the accepted doctrine of the dominant school of geology. Besides, within certain limits and in certain lights, the arguments of the uniformitarian and of the physicist might hold good—that is to say, if we would restrict the deductions of the former to the recent period, and could adopt the propositions of the latter. Our part, however, is to see whether their conclusions agree—not with their respective assumptions, but with the geological evidence: for no conclusions can be accepted that do not meet with the full concurrence of all the copartners interested in the result, and without respect for their mutual claims progress is not possible. The geologist must attend to the claims of the physicist, and the physicist ought not to overlook those of the geologist. How then stands the case?
With regard to the geological problem, we are told by the uniformitarians that the forces acting on the surface of the globe have been in all past times the same, both in kind and degree, as those now in operation. On those grounds they have proceeded to estimate, first, the time required for mountain and continental elevation; secondly, the rate of erosion of the valleys, and of the denudation or lowering of the land. Their conjecture is that our limited experience of two thousand to three thousand years has sufficed to furnish us with instances of all the various vicissitudes and changes that the earth has undergone during the illimitable past a generalization incompatible with what is known of the evolution of the earth, and in contradiction to their own premises. For even geologists who recognize no change admit the original molten state of the globe. This of itself involves, in the cooling of the mass, the intervention of stresses and strains, with all their consequences, which render it inconceivable that there was nothing in all those stages of the earth's history beyond what our limited experience has brought us in contact with.