Imagens das páginas

any written documents whatever. The domestic manners of the Egyptians have been clearly made out by an examination of that picture-writing which has been called hieroglyphic; and in the same way the careful observation and comparison of the figures painted on vases or sarcophagi has thrown light upon a similar subject of research, with regard not only to the ancient Greeks, but even the Etruscans, of whom at best we know very little, and absolutely nothing by any direct historical documents. The knowledge thus acquired indirectly is however valuable, because it may generally be thoroughly depended on; and if the facts so determined appear at first sight few and unimportant, they are found from time to time to possess an increasing value, and they are the more credible as being for the most part too unimportant in themselves to have been worth while to falsify.

Now, in a way not much unlike that which must be pursued in investigating this kind of history, it is possible to make out an account of the successive events that have taken place in various parts of the world, not only before the earth was inhabited by civilized men, but even when man had not yet been created.

Since however, before attempting to give a history of a people, it must be perfectly certain that the people to be spoken of did once exist, so the reader has a right to require that, before commencing, as I propose to do, an account of the pre-adamite world, it should be clearly shown that there exist for this account the true materials of history; and that there is, in fact, that degree of order and system in the

arrangement of the different parts of the earth's crust, without which there could be no connected or reasonable account of events.

The proof of such a condition is, however, at hand, and requires only that the very commonest appearances of nature should be studied. No one can visit a chalk or sand pit, or look for one moment at a stone quarry, no one can consider the appearances so commonly presented by a sea-cliff, a cutting for a road, or a sinking for a well, without being perfectly convinced that the limestones, sandstones, and clays, of which a great part of the earth's crust is made up, were not thrown confusedly together, but are arranged in some degree of order, lying upon one another in regular beds or strata. A very little inquiry into the way in which these strata rest upon one another, is amply sufficient to prove that order does exist in the arrangement of the greater proportion of the materials of the earth's crust; and the more strictly this inquiry is carried out, the more convinced will the observer become of the great fact, that there is a history to be learnt-a succession of events to be described.

But it may be said, and with great reason, that the mere fact of order in the arrangement of these superficial materials proves nothing more than that they were deposited in succession, and they might either have been so placed at the first creation of the world, or, since the whole bears marks of aqueous action and of disturbance, that the successive beds may have arranged themselves as we find them during some great deluge. But the possibility of this is contradicted by appearances presented to the observer of nature at every turn, and by the result of every investigation,

however superficial, when the actual structure of the earth is laid open, whether in the quarry or the sea-cliff.

There are, indeed, so many distinct facts that prove both the nature of the deposits and the circumstances of deposition to have been very different from either a creation of the surface as it now exists, or the formation of such a surface by a deluge, that it is more easy to be confused with their number and variety, than to resist the conclusion when the reason is fairly appealed to. Among these facts we may perhaps select these three with advantage, as the most prominent, viz. (1.) That a vast number of strata may be discovered to rest on one another, and that they are of very great thickness and extent, and exhibit great variety both in the nature and condition of the materials of which each is made up; (2.) That the beds are found, in many cases, not lying regularly upon one another, but showing by their direction and inclination that one series has had time to harden, and be disturbed in position, before another was placed upon it; and (3.) That almost throughout the whole great and varied series of strata there are found the remains of a number of animals of different kinds, chiefly but not entirely of marine origin; each group of which presents in itself a history, and denotes a peculiar condition, both of the depth of the water, and the structure of the sea-bottom especially adapted for it. The proper consideration of the three facts, or rather classes of facts, thus alluded to, cannot fail to satisfy any one that the strata of the earth's crust were formed gradually and slowly, under various circumstances, and at different times. I do not mean,

however, now to illustrate these facts at any length, because, in truth, they would involve the whole subject of Descriptive Geology, and would require the introduction of details, and the use of technical language, which it is my especial object to avoid. The reader must either take for granted that there are such facts, or he may satisfy himself concerning them by a very slight amount of observation and investigation.

Although, however, the following pages may not communicate any such argumentative proofs of the truth of Geological conclusions as would be required to convince those who are determined to doubt, yet actual observations will be presented to the notice of the reader in order, and the conclusions which alone seem rational will be narrated as history. My object in alluding to the series of investigations on which the science of Geology is founded, is rather to show how far there are supposed to exist materials for description and history, than to enter into any discussion or argument concerning these materials. It is enough that I have alluded to the nature of the facts, and the kind of observations required.

Taking it for granted, then, that there is something in the structure of the earth which requires and admits of investigation, let us next see how far this investigation can be carried with reason, and how far the structure of the globe is laid open for examination. The reader must indeed be contented to take upon trust the statements that will be made in this introductory chapter concerning Descriptive Geology, but he may be assured that they are too well established, and founded on too many observations, to be shaken, or even questioned.

In the first place, then, there is the evidence of what are called 'Geological sections;' offering sufficient proof that the different strata of which the earth's crust is composed are of certain limited extent and thickness, and that they overlie one another in regular order.

Fig. 1


This kind of evidence reaches indeed farther, and proves very sufficiently that there is some characteristic mark of each group of strata by which it may be known and recognised; so that the kind of sandstone, limestone, or clay beds that may exist in one part of the series, and the order in which they succeed each other, is not so closely imitated in another part, but that a distinction may generally be drawn without much difficulty. Geological sections, and the maps which should accompany them, prove also in addition to this, that over large tracts of country, and even over whole continents, the same invariable order of arrangement of the strata may be traced; so that the Geologist is thus enabled to advance with some confidence, and frame those generalizations with. out which Geology could hardly exist as a science.

Besides this evidence, derived from the examination of the mere mineral materials of which strata are composed, there is however another, and a far more important means of acquiring a knowledge of the earth's history, derived from the study of the animal and vegetable remains that are found in almost every one of the

« AnteriorContinuar »