« ZurückWeiter »
heat or light, but only decompose a substance, which received it originally as a part of its composition? Heat may be thus considered as originally in a fluid state; but, attracted by organized bodies in their growth, becomes a part of the solid. Besides this, I can conceive, that in the first assemblage of the particles of which this earth is composed, each brought its portion of the loose heat that had been connected with it, and the whole, when pressed together, produced the internal fire that still subsists.
QUERIES AND CONJECTURES RELATING TO MAGNETISM AND THE THEORY OF THE EARTH.
To Mr. Bodoin. DEAR SIR, I Received your favours by Messrs. Gore, Hilliard, and Lee, with whose conversation I was much pleased, and wished for more of it; but their stay with us was too short. Whenever you recommend any of your friends to me, you oblige me.
I want to know whether your Philosophical Society received the second volume of our Transactions. I sent it; but never heard of its arriving. If it miscarried, I will send another. Has your Society among its books the French work sur les Arts, et les Metiers? It is voluminous, well executed, and may be useful in our country. I have bequeathed it them in my will; but if they have it already, I will substitute something else.
Our ancient correspondence used to have something philosophical in it. As you are now more free from public cares, and I expect to be so in a few months, why may we not resume that kind of correspondence? Our much regretted friend Winthrop once made me the compliment, that I was good at starting game for philosophers: let me try if I can start a little for you.
Has the question, 'How came the earth by its magnetism,' ever been considered?
Is it likely that iron ore immediately existed when this globe was first formed; or may it not rather be supposed a gradual production of time?
If the earth is at present magnetical, in virtue of the masses of iron ore contained in it, might not some ages pass before it had magnetic polarity?
Since iron ore may exist without that polarity, and by being placed in certain circumstances may obtain it from an external canse, is it not possible that the earth received its magnetism from some such canse?
In short, may not a magnetic power exist throughout our system, perhaps through all systems, so that if men could make a voyage in the starry regions, a compass might be of use? And may not such universal magnetism, with its uniform direction, be serviceable in keeping the dinrnal revolution of a planet more steady to the same axis?
Lastly, as the poles of magnets may be changed by the presence of stronger magnets, might not, in ancient times, the near passing of some large comet of greater magnetic power than this globe of ours have been a means of changing its poles, and thereby wreckmg and deranging its surface, placing in different regions the effect of centrifugal force, so as to raise the waters of the sea in some, while they were depressed in others?
Let me add another question or two, not relating indeed to magnetism, but, however, to the theory of the earth.
Is not the finding of great quantities of shells and bones of animals (natural to hot climates) in the cold ones of our present world, some proof that its poles have been changed? Is not the supposition that the poles have been changed, the easiest way of accounting for the deluge, by getting rid of the old difficulty how to dispose of its waters after it was over? Since if the poles were again to be changed, and placed in the present equator, the sea would fall there about fifteen miles in height, and rise as much in the present polar regions; and the effect would be proportionable, if the new poles were placed any where between the present and the equator.
Does not the apparent wreck of the surface of this globe, thrown up into long ridges of mountains, with strata in various positions, make it probable that its internal mass is a fluid—but a fluid so dense as to float the heaviest of our substances? Do we know the limit of condensation air is capable of? Supposing it to grow denser within the surface, in the same proportion nearly as it does without, at what depth may it be equal in density with gold?
Can we easily conceive how the strata of the earth could have been so deranged, if it had not been a mere shell supported by a heavier fluid? Would not such a supposed internal fluid globe be immediately sensible of a change in the situation of the earth's axis, alter its form, and thereby burst the shell, and throw up parts of it above the rest? As, if we would alter the position of the fluid contained in the shell of an egg, and place its longest diameter where the shortest now is, the shell must break; but would be much harder to break, if the whole internal substance were as solid and hard as the shell.
Might not a wave, by any means raised in this supposed internal ocean of extremely dense fluid, raise, in some degree, as it passes, the present shell of incumbent earth, and break it in some places, as in earthquakes? And may not the progress of such wave, and the disorders it occasions among the solids of the shell, account for the rumbling sound being first heard at a distance, angmenting as it approaches, and gradually dying away as it proceeds? A circumstance observed by the inhabitants of South America in their last great earthquake; that noise coming from a place some degrees north of Lima, and being traced by inquiry quite down to Buenos Ayres, proceeded regularly from north to south at the rate of leagues per minute, as I was informed by a very ingenious Peruvian, whom I met with at Paris.
ON THE NATURE OF SEA COAL. To M. Dubourg.
* * * I Am persuaded, as well as you, that the sea coal has a vegetable origin, and that it has been formed near the surface of the earth; but as preceding convulsions of nature had served to bring it very deep in many places, and covered it with many different strata, we are indebted to subsequent convulsions for having brought within our view the extremities of its veins, so as to lead us to penetrate the earth in search of it. I visited last summer a large coal-mine at Whitehaven, in Cumberland; and in following the vein, and descending by degrees towards the sea, I penetrated below the ocean, where the level of its surface was more than eight hundred fathoms above my head; and the miners assured me that their works extended some miles beyond the place where I then was, continually and gradually descending under the sea. The slate, which forms the roof of this coal mine, is impressed in many places with the figures of leaves and branches of fern, which undoubtedly grew at the surface when the slate was in the state of sand on the banks of the sea. Thus it appears that this vein of coal has suffered a prodigious settlement. • • •