The reader has now before him a general outline of Geological theory, together with some familiar illustrations of the evidence by which it is supported. We shall not attempt to enforce this evidence by any remarks of our own. Indeed it is of a kind that can derive but little aid from the arts of logic or rhetoric. It needs but to be fairly understood, and if it does not altogether compel our assent, it begets at least a presumption so strong as to leave little room for doubt or hesitation. Nobody, so far as we know, has ever hesitated to believe that the Round Towers of Ireland are the work of human hands. And yet if some incredulous skeptic were to raise the cry against this common opinion, were to argue that it is a mere hypothesis, and call for proof, we should be embarrassed how to answer him. We could only say that these monuments have all the characteristic marks of man’s handiwork; and that buildings of this kind have never been known to come into existence except through the agency of Man. But should our vexatious skeptic contend that they were possibly produced by a freak of Nature; or that they were built in the beginning by the Creator of the World, who certainly might have made them had He been so minded, we should think him very unreasonable, and probably not feel much disposed to prolong the discussion. In like manner the theory of Geology which we are defending, cannot be established by a rigid demonstration; but we believe there is not one man of sense and judgment, who, being fully master of the evidence on which it rests, hesitates to accept that theory, at least in its more general outlines. No doubt many able and eminent men are to be found arrayed against Geology; but it would be easy to show from their writings that they have never thoroughly examined the facts about which they talk so flippantly, and which they often set aside so lightly.