Geology, so far as our present subject is concerned, stands upon a somewhat different footing. Though a much younger science than astronomy, it has one great advantage over it; the facts with which it has to do are for the most part discernible by the unaided senses, and it is therefore independent of instrumental help. Many changes have occurred in the views of Geologists, but in the main they have reference to processes [Footnote: Such, for instance, is the modification of the views of geologists as to the relative effects of "disruption" and "denudation" in determining the features of the earth's surface.] rather than to results, and it is the results with which we are chiefly concerned. Physiologists have entered on the contest with the Bible on two different, and seemingly contradictory grounds. Some of them have maintained that the varieties of mankind are so distinct, that it is impossible they can all be descended from a single human pair, while others assert that not only all the varieties of mankind, but all the varieties of living beings are descended from a single progenitor. Between the advocates of these two systems there must be such an enormous difference as to the extent to which variation is possible, as to justify us in assuming that the fundamental principles of physiological science are not yet satisfactorily ascertained. These are the three branches of science which come especially into collision with the Mosaic Record of the Creation. Of these Geology is the most important, because it is able to bring forward unquestionable facts which are in direct opposition to the traditionary interpretation Astronomy and physiology have little to object except theoretical views; the hypotheses of Laplace and Darwin. These, however, will have to be carefully considered. It will be necessary for us first to ascertain whether there really exists any such fundamental discrepancy between the record and ascertained facts, or theories so far as they are supported by facts, and stand on a probable footing, as should render all attempts at harmonizing them vain. If this is found not to be the case, we shall then be in a position to inquire whether modern discoveries afford us any really valuable light, and can assist us to form a somewhat more extended and accurate idea of the processes described by the sacred historian. CHAPTER II. DIFFICULTIES IN GEOLOGY. The principal points on which there is a supposed discrepancy between the Mosaic Record and the discoveries of geologists are as follows:-- THE MOSAIC RECORD APPEARS TO ASSERT-- I. That the world in all its completeness, as it now exists, was moulded out of material in a chaotic state in six ordinary days. Geologists have ascertained, beyond the possibility of a doubt, that the process must have occupied countless ages.