and chemical, geographical—and biological and throws it on the pages of that Great Stone Book on which the past history of our globe is recorded. And while Astronomy is of all sciences that which may be considered as most nearly representing Nature as she really is, Geology is that which most completely represents her as seen through the medium of the interpreting mind; the meaning of the phenomena that constitute its data being in almost every instance open to question, and the judgments passed upon the same facts being often different according to the qualifications of the several judges. No one who has even a general acquaintance with the history of this department of science can fail to see that the geology of each epoch has been the reflection of the minds by which its study was then directed; and that its true progress dates from the time when that "common-sense" method of interpretation came to be generally adopted which consists in seeking the explanation of past changes in the forces at present in operation, instead of invoking the aid of extraordinary and mysterious agencies, as the older geologists were wont to do whenever they wanted—like the Ptolemaic astronomers—"to save appearances." The whole tendency of the ever-widening range of modern geological inquiry has been to show how little reliance can be placed upon the so-called "laws" of stratigraphical and paleontological succession, and how much allowance has to be made for local conditions. So that, while the astronomer is constantly enabled to point to the fulfilment of his predictions as an evidence of the correctness of his method, the geologist is almost entirely destitute of any such means of verification. For the value of any prediction that he may hazard—as in regard to the existence or non-existence of coal in any given area—depends not only upon the truth of the general doctrines of geology in regard to the succession of stratified deposits, but still more upon the detailed knowledge which he may have acquired of the distribution of those deposits in the particular locality. Hence no reasonably-judging man would discredit either the general doctrines or the methods of geology, because the prediction proves untrue in such a case as that now about to be brought in this neighborhood to the trial of experience.
We have thus considered man's function as the scientific interpreter of Nature in two departments of natural knowledge, one of which affords an example of the strictest and the other of the freest method which man can employ in constructing his intellectual representation of the universe. And, as it would be found that in the study of all other departments the same methods are used either separately or in combination, we may pass at once to the other side of our inquiry—namely, the origin of those primary beliefs which constitute the groundwork of all scientific reasoning.
The whole fabric of geometry rests upon certain axioms which every one accepts as true, but of which it is necessary that the truth should be assumed, because they are incapable of demonstration. So,
