are upon a thorough cleaning, the first dirty thing to be removed is one's husband. I am called for

again. Adieu.

ON THE THEORY OF THE EARTH.

SIR,

TO ABBE SOULIAVE.

I RETURN the papers with some corrections. I did not find coal mines under the calcareous rock in Derbyshire. I only remarked, that at the lowest part of that rocky mountain which was in sight, there were oyster-shells mixed with the stone; and part of the high country of Derby being probably as much above the level of the sea as the coal-mines of Whitehaven were below, it seemed a proof that there had been a great bouleversement in the surface of that island, some part of it having been depressed under the sea, and other parts, which had been under it, being raised above it. Such changes in the superficial parts of the globe seemed to me unlikely to happen, if the earth were solid at the centre. I therefore imagined that the internal parts might be a fluid more dense, and of greater specific gravity than any of the solids we are acquainted with; which therefore might swim in or upon that fluid. Thus the surface of the globe would be a shell, capable of being broken and disordered by the violent movements of the fluid on which it rested. And as air has been compressed by art so as to be twice as dense as water, in which case, if such air and water could be contained in a strong glass vessel, the air would be seen to take the lowest place, and the water to float above and upon it; and, as we know not yet the degree of density to which air may be compressed, and M. Amontons calculated,

that its density increasing as it approached the centre in the same proportion as above the surface, it would, at the depth of leagues, be heavier than gold, possibly the dense fluid occupying the internal parts of the globe might be air compressed. And as the force of expansion in dense air when heated, is in proportion to its density, this central air might afford another agent to move the surface, as well as be of use in keeping alive the central fires; though, as you observe, the sudden rarefaction of water, coming into contact with those fires, may be an agent sufficiently strong for that purpose, when acting between the incumbent earth and the fluid on which it rests.

If one might indulge imagination in supposing how such a globe was formed, I should conceive, that all the elements in separate particles, being originally mixed in confusion, and occupying a great space, they would (as soon as the Almighty fiat ordained gravity, or the mutual attraction of certain parts, and the mutual repulsion of other parts, to exist) all move towards their common centre; that the air being a fluid whose parts repel each other, though drawn to the common centre by their gravity, would be densest towards the centre, and rarer as more remote; consequently, all bodies, lighter than the central parts of that air, and immersed in it, would recede from the centre and rise till they arrive at that region of the air, which was of the same specific gravity with themselves, where they would rest; while other matter mixed with the lighter air, would descend, and the two, meeting, would form the shell of the first earth, leaving the upper atmosphere nearly clear. The original movement of the parts towards their common centre

would form a whirl there: which would continue in the turning of the new-formed globe upon its axis, and the greatest diameter of the shell would be in its equator. If by any accident afterward the axis should be changed, the dense internal fluid, by altering its form, must burst the shell, and throw all its substance into the confusion in which we find it. I will not trouble you at present with my fancies concerning the manner of forming the rest of our system. Superior beings smile on our theories, and at our presumption in making them. I will just mention that your observation of the ferruginous nature of the lava which is thrown out from the depths of our volcanoes, gave me great pleasure. It has long been a supposition of mine, that the iron contained in the substance of the globe has made it capable of becoming, as it is, a great magnet; that the fluid of magnetism exists perhaps in all space; so that there is a magnetical North and South of the universe, as well as of this globe; and that if it were possible for a man to fly from star to star, he might govern his course by the compass: that it was by the power of this general magnetism this globe became a particular magnet. In soft or hot iron the fluid of magnetism is naturally diffused equally; when within the influence of a magnet, it is drawn to one end of the iron, made denser there and rarer at the other. While the iron continues soft and hot, it is only a temporary magnet; if it cools or grows hard in that situation, it becomes a permanent one, the magnetic fluid not easily resuming its equilibrium. Perhaps it may be owing to the permanent magnetism of this globe, which it had not at first, that its axis is at present kept parallel to itself, and not liable to the changes it

formerly suffered, which occasioned the rupture of its shell, the submersions and emersions of its lands, and the confusion of its seasons. The present polar and equatorial diameters differing from each other near ten leagues, it is easy to conceive, in case some power should shift the axis gradually, and place it in the present equator, and make the new equator pass through the present poles, what a sinking of waters would happen in the present equatorial regions, and what a rising in the present polar regions; so that vast tracts would be discovered that now are under water, and others covered that now are dry, the water rising and sinking in the different extremes nearly five leagues! Such an operation as this possibly occasioned much of Europe, and, among the rest, of this mountain of Passy, on which I live, and which is composed of limestone, rock, and sea-shells, to be abandoned by the sea, and to change its ancient climate, which seems to have been a hot one. The globe being now become a perfect magnet, we are perhaps safe from any future change of its axis. But we are still subject to the accidents on the surface, which are occasioned by a wave in the internal ponderous fluid and such a wave is produced by the sudden violent explosion you mention, happening from the junction of water and fire under the earth, which not only lifts the incumbent earth that is over the explosion, but impressing with the same force the fluid under it, creates a wave that may run a thousand leagues, lifting, and thereby shaking successively, all the countries under which it passes.

WILLIAM WALKER, PRINTER, OTLEY.