himself gives motion and action, without entrusting the conduct to our care, he has concealed from our knowledge. For example, we are ignorant of the structure of our stomach, because God has eased us of the care of its digestion. In vain would the most able anatomist direct his digestion; all very often goes contrary to his wishes. On the other hand, we have in our senses many watchful and faithful monitors, opportunely to direct what nourishment is proper for us. Why then have we so many methods to be acquainted with our nutriment, if it is not that the care of seeking and chusing it, is committed to us? And why, on the contrary, do we not know how to digest, if it be not that God has evidently willed our digestion to be performed in us without our direction? God, who has spared us that trouble, has denied us the knowledge of the mechanism which forms the flesh and the fruits that we eat, as well as the mechanism which extracts the juices from them for our nourishment, This knowledge would have distracted us. We attain the age of four score and ten, without knowing what digestion is, or what is the action of the muscles. We have been served without any care on our part. Had we thoroughly known the structure of our stomachs, we should have been for directing its functions. God has not allowed this knowledge to man. He ordained him to be otherwise employed. If then this mechanism be hid from him, lest it should multiply his cares, will he acquaint him with the structure of the world, the motion of which is not committed to his charge?

I can scarcely be of opinion, that the modern philosophers have rightly conceived the plan of the Creator, in having less esteem for the knowledge which we attain by our senses, than for what they imagine is to be acquired by a profound meditation. One example will make me understood.

The common sailor knows nothing more of the loadstone than what his senses inform him, viz. its tendency towards the north pole. This is the sum of his knowledge. The philosopher would know the cause of this phenomenon; he employs the effluvia of its pores in spiral lines, the attractions, the repulsions; and after several years use of his mechanics, his geometries and calculations, he either acknowledges that he himself knows nothing of the matter, or else has the mortification to find that nobody approves of his system. The systematical philosopher, who thinks himself ignorant if he know not the cause of what he sees, passes his whole life in the pursuit of possibilities, and becomes useless to the rest of mankind by being buried

alive in his closet. The sailor makes use of what his senses inform him of, the direction of the loadstone towards the north, and by its assistance voyages to the end of the world. Make choice of ten thousand other informations of fact, and you will hardly find one of them but what is of service. Our fortunes will be better in proportion to this sort of knowledge. Would you seek after the causes of these effects? You will meet with nothing of certainty or use. Can we, after this, mistake the intention of God, in the measure of understanding which he affords us for our present instruction?

It is evident that we have no universal knowledge. The objects of our pursuit are scattered round us upon the earth and in the heavens. God has given us, together with eyes and understanding, a fund of curiosity which stimulates us from one object to another, that new experiments may enable us to procure new conveniencies for our brethren; and that every thing upon earth may, by degrees, be put to the best use for the profit of mankind. But though a man can go on a stretch from Brest to Pekin, it does not follow that he can go to the moon; or though he have a principle of power in his hands, that enables him to support piles of oak, and great blocks of marble in the air, this is no reason why he should attempt with his levers to make the moon fly off from her orbit, or to fix his pullies to the body of Jupiter, to rob him of one of his satellites. As man's strength is limited, so likewise is his knowledge, and these bounds are suited to his wants. He meets with opposition every where, when he enters upon idle speculations. But he proceeds from discovery to discovery, which discoveries work miracles, when he employs himself in making the best use of that which is about him. Our reason is always attended with success in uniting the truths of experience with the necessities of life, in making a prudent use of the benevolence of the Creator, and in giving him the glory. This is the sum Lotal of human knowledge.

[Abbé Le Pluche. Spec. de la Nature.]

We have given the above, not because we approve of the philosophy of the vortices, but as containing a tolerably fair view of the theories that preceded it; and a curious specimen of the different modes by which this philosophy was adhered to, in opposition to the doctrine of universal attraction, as long as it could possibly be defended.-Editor.

BOOK II.

GEOLOGY.

CHAPTER I.

GEOGNOSY; OR, THE DOCTRINE OF THE ORIGIN AND GENERAL STRUCTURE OF THE EARTH.

UNDER

NDER the Wernerian system of Mineralogy, the term Geology is altogether relinquished, or only incidentally referred to, as importing abstract and imaginary speculations concerning the formation of the Earth: while the immediate branch of science, designed to be glanced at in the present chapter, is denominated Geognosy. We have no objection to the last term in the sense thus signified; but shall restore the term Geology, and employ it, as its derivation will readily justify our doing, in a classific form, importing the general doctrine of the earth in its insentient or unorganized frame; and consequently as comprising equally its subterranean, superficial, and atmospherical phænomena.

Before we enter, however, upon these particular parts of our subject, it becomes us to offer a brief view of what, so far as we are capable of determining from an actual survey of nature, appears to have been the origin of the earth, as to its present structure and constitution, comprising that introductory branch of geological science, which, as we have already observed, professor Werner has distinguished by the name of Geognosy.

The object of Geognosy is to unfold the general make of the globe; to discover by what causes its parts have been arranged; from what operations have originated the general stratification of its materials, the inequalities with which its surface is diversified,

and the immense number of different substances of which it is composed,

In pursuing this investigation, many difficulties occur to us. The bare surface or mere crust of the solid substance of the earth is the whole that we are capable of boring into, or of acquiring a knowledge of, even by the deepest clefts of volcanoes, or the bottoms of the deepest seas. It is not often, however, that we have a possibility of examining either seas or volcanoes at their bottom; the inhabitable part of the globe bears but a small portion to the unin habitable, and the civilized an infinitely smaller proportion still. Hence, our experience must be necessarily extremely limited; a thousand facts may be readily conceived to be unfolded that we are incapable of accounting for, and a variety of theories are daily disappearing while other theories are starting up in their stead.

So far as the superficies of the earth has been laid open to us by ravines, rivers, mines, &c. we find it composed of stony masses, sometimes simple, as lime-stone, serpentine, or quartz; but more frequently compound, or composed of two or more simple materials, variously mixed and united together, as granite, which is a composition of quartz, felspar, and mica. These stony masses, or rocks, are numerous, and they appear to be laid one over the other, so that a rock of one kind of stone is covered by another species of rock, and this by a third, and so on. In this superposition of rocks, it is easily observable, that their situation is not arbitrary; every stratum occupies a determinate place, so that they follow each other in regular, order from the deepest part of the earth's crust, which has been examined, to the very surface. Thus there are two things respecting rocks, that peculiarly claim our attention; their composition and their relative situation. But, besides the rocks which constitute the earth's crust, there are other masses which must also be considered. These traverse the rocks in a different direction, and are known by the name of veins, as if the rocks had split asunder in different places from top to bottom, and the chasins had been afterwards filled up with the matter which constitutes the vein.

Independently of the substances thus presented to us, we meet with facts that prove most decisively that the general mass has undergone various revolutions at various times, and revolutions not only of great antiquity, but of universal extent, We have the most

unexampled proof, that its whole surface has been covered with water, and that every part of it has suffered change; mountains have been raised, plains levelled, islands separated from a continent, and the waters collected so as to leave an elevated land. We find

it difficult to conceive causes adequate to the production of such effects; and operations so immense seem too remote from any means of investigation which we possess, to admit of being explained.

One point, however, in the midst of all the intricacy that surrounds us still remains decided, that the shell of the globe has, at some period or other, been in a state of fluidity, and that from "this circumstance has arisen its present arrangement. Now the only two causes that can enter into the mind of man as being competent to such an effect are, the operation of fire, or of some solvent; and hence our researches become in some degree limited to the inquiry by which of these means this effect has been induced. If a solvent have been the cause, that solvent must have been water, for there is no other fluid in nature in sufficient abundance to have acted the part of a solvent upon a scale so prodigious.

Hence, then, two distinct theories arise, which appear to have been agitated with considerable warinth in former times, but with a much greater degree of warmth, and much deeper view of the subject, in the present day. Is the present structure of the solid contents of the earth, so far as it is capable of examination, the result of igneous fusion, or of aqueous solution? Is the Plutonic or the Neptunian system founded on the strongest basis? In ancient times Heraclitus took the lead as to the former; and Thales, or rather, perhaps, Epicurus, as to the latter. In our own period, though the Plutonic theory was first revived by M. Buffon, or rather perhaps by Hooke, its defenders are now chiefly confined to our own country, and consist of Dr. Hutton, professor Playfair, and very lately of Sir James Hall; names unquestionably highly respectable, and entitled to every deference, but most powerfully opposed by the respectable authorities of Werner, De Saussure, and Kirwan, not to mention that the general voice of geologists is very considerably in favour of the Neptunian theory, or that entertained by the lastmentioned philosophers.

Plutonic Theory.-1. According to this system there is in the substance either of the entire globe, or throughout the entire crust