In pursuing this investigation two points must be carefully kept in mind; the first is the distinction between theory and conjecture on the one hand, and well ascertained facts on the other. We shall have much to do with theory, and with conjectural interpretations of observed facts. These can never stand on the same footing as the facts themselves, but can only be regarded as invested with greater or less probability. If it is found that these theories do explain many observed facts, that they harmonize with, and as it were dovetail into any proposed interpretation of which the words of Moses are capable; and still more if that interpretation actually completes the defective points of the theories, and supplies an adequate cause for facts hitherto inexplicable--then the presumption is a very strong one that the interpretation thus supported is at all events an approximation to the true one. The second point to be carefully kept in mind is the very imperfect state of scientific knowledge even at the present time. As far as the matter in hand is concerned, the facts which are ascertained beyond all possibility of doubt, are very few. New means of investigation have very recently been discovered, and as a consequence new sources of information have been pointed out, new fields of research have been laid open. Twenty years ago the spectroscope was a thing undreamt of--now astronomers reckon it as of equal value with the telescope, while chemists find it indispensable to their researches. Who shall say that the next twenty years may not witness some invention of equal importance, which shall throw upon us a fresh flood of light from some unexpected quarter? If then the principle which has hitherto been maintained is correct, that all our difficulties arise from interpretations based upon insufficient knowledge, but maintained as if of equal authority with the record itself, there is a great danger lest after a time the same difficulty should recur--that the discovery of fresh facts may discredit interpretations based upon our present knowledge. Any interpretation therefore to which we may be led by the scientific views at present entertained, must be regarded as only provisional and tentative, liable at any time to be either confirmed, amended, or rejected, as fresh discoveries may be made. Before we enter upon a detailed examination of the records of the several days, there are two preliminary points to which attention must be directed. We shall have to make frequent reference to "law." It will be well that the sense in which the term is used should be made clear. The account of the First Day's Work will lead to the recent theory of the Correlation of Forces. As this is probably a new subject to many, some previous explanation of it will be necessary. SECTION 1. OF LAW. [Footnote: This subject is fully treated in the Duke of Argyll's "Reign of Law."]