the principal kinds of which have almost every where the same order of superposition. 2dly. After the first kinds of strata, visibly the most ancient, and containing no organic bodies, we find other strata wherein such bodies are contained, and these change their species in the strata of different kinds which are placed one above another. 3dly. We find remains of terrestrial animals and vegetables among these organic bodies: but in the great majority of these strata, and even in the loose strata at the surface of our soil, the most considerable part consists of marine bodies. 4thly. Although it is thus certain that our strata were formed in the sea, (which necessarily implies that they must have been accumulated in a continuous manner, and in a situation nearly horizontal) they are actually broken, overthrown, and sunk in great masses, in such a manner that the whole surface of our continents exhibits the most ruinous appearance. 5thly. The violent causes which have thus disordered our strata preceded some great revolution, by which our continents were left dry, and thus submitted to the operation of such causes as are at present known. 6thly. This great event was not many ages prior to the times traced back by human monuments.

36. Such are the general facts which, as certain and determined effects of causes that have formerly operated on our globe, mark out the task of the geologist; and, to embrace the whole subject, he must of necessity explain, 1st. The origin of the substances of which our strata are composed. 2dly. The cause of the successive differences which we observe in these substances. 3dly. Why it is that remains of terrestrial animals and vegetables are found, in some strata,

intermixed with those of marine animals. 4thly. Whence proceeds the disorder of these strata, and the dispersion of their fragments. 5thly. By what means their ruins are now found above the level of the sea. 6thly, and finally, To what changes these ruins have been exposed, from causes actually known, since they have emerged from the sea.

This, Sir, is the task I have undertaken in my Letters to the Journal de Physique; and, in my ensuing Letters, I shall have the honour to lay before you a sketch of the causes to which I attribute this series of events, as well as of their connection with what Revelation has taught mankind respecting the history of the earth and of the universe.

I have the honour to be, &c.

LETTER II.

Analysis of Geological Phenomena, leading to a determination of their Origin.

Windsor, June 27, 1793.

I HAVE stated in my first Letter, from the most striking phenomena of the earth, the task traced out for those who undertake its history, and which I have prescribed to myself accordingly. But before entering upon it, I shall offer a few remarks upon the conduct of some persons of a high rank among naturalists respecting this subject.

1. It is an assertion we very frequently hear made, that human nature is becoming daily more enlightened. And, it may seem to be an assertion too true to leave room for any doubts: it is, however, equivocal, and to admit it without proper examination, would lead to the most mischievous consequences. To this point, I shall now direct my observation.

And first, it is essential to remark, that knowledge, considered as the result of the observations and enquiries of man, divides itself into two branches, different in their nature, and which do not always keep pace with each other: the one is, the collection of axioms

and facts, which are in themselves independent of man, and are supplied from objects without us; the other is, the collection of theories or systems deduced from these data. It is therefore under these two points of view, separately considered, that we must examine the scientific progress of any particular age.

2. Moreover, in such an examination, the general object of knowledge presents itself under two very different aspects; for we must be careful not to confound that portion of real knowledge which we may find among a select number of individuals, with the sum of what may be found diffused among the rest of mankind; nor the judgment pronounced on their discoveries, by those to whom they are due, with the mode whereby they are made known by those who merely repeat them. Even when new discoveries take place, they are seldom at first pure from error; time is required that they may be examined, corrected, and accurately determined, by a certain class of individuals; to this test they must be submitted before they can be entitled to be received into the stock of true knowledge. But, very often, the new ideas which are disseminated, are either but glimmerings of light, or perhaps false views of new objects, which, for a time, and occasionally in circumstances the most important to mankind, is worse than a total want of knowledge. When our age is complimented with being more enlightened than preceding ones, allusion is made to a knowledge that we find generally diffused; and consequently it is on this ground, that I am called to examine the question.

3. In every age, the learned form a distinct class of men to whom science is supposed to owe its preserva

tion and progress, and whose peculiar province it is to instruct others in those matters, which for want either of time, or opportunity, or suitable means, they are unable to discover and study themselves. If their instructions were limited to facts, without the addition of commentaries, science thus disseminated among mankind, would, while it augments, always continue real; but the human mind is prone to generalize; to conclude that to be common and constant, which has only been occasionally observed, in order to connect it sooner and more easily with some ideas of causes ; and thus it frequently happens that when new discoveries are made, facts are so blended with hypotheses, that at first they are confounded together: so that they who cannot or will not receive any instruction but such as is easy, and requires little attention and reflection, can hardly fail to fall into error. It is plain, then, that we should judge hastily to pronounce an age enlightened, merely because we hear much talk of knowledge in it; it is necessary first to ascertain in what this knowledge consists.

4. The more facts multiply at any particular period, the more time is required to disengage these new facts from the several hypotheses (implied or expressed) with which those who first announce them to the world are apt to accompany them. Thus the abundance of facts which may be collected in any particular age, must not be considered in itself as a sign of a proportionable increase of true knowledge: it may be diminished, and even false views substituted in its stead, by want of precision in distinguishing facts and consequences from the hypotheses that accompany