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 the 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 are now dry, the water rising and sinking in the different extremes near five leagues. Such an operation as this possibly occasioned much of Europe, and among the rest this Mountain of Passy on which I live, and which is composed of limestone, rock, and seashells, 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 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 producible 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. I know not, whether I have expressed myself so clearly, as not to get out of your sight in these reveries. If they occasion any new inquiries, and produce a better hypothesis, they will not be quite useless. You see I have given a loose to imagination; but I approve much more your method of philosophizing, which proceeds upon actual observation, makes a collection of facts, and concludes no farther than those facts will warrant. In my pres

ent circumstances, that mode of studying the nature of the globe is out of my power, and therefore I have permitted myself to wander a little in the wilds of fancy. With great esteem,

I have the honor to be, Sir, &c.
B. FRANKLIN.

P. S. I have heard, that chemists can by their art decompose stone and wood, extracting a considerable quantity of water from the one, and air from the other. It seems natural to conclude, from this, that water and air were ingredients in their original composition; for men cannot make new matter of any kind. In the same manner may we not suppose, that, when we consume combustibles of all kinds, and produce heat or light, we do not create that 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.

FROM JOHN INGENHOUSZ TO B. FRANKLIN.

Experiment for burning Wire.

Vienna, 29 November, 1782.

I send you a wire, folded up in a spiral, which you must arrange as you see the wire on the figure I join to it. Leave at the end of it the bit of agaric. When you have a bottle of white glass, of about a pint or more, filled with good dephlogisticated air, take away the cork, and clap your thumb of the left hand on the orifice. In the mean time, turn for a moment the bit of agaric in the flame of a candle, till you see it is everywhere kindled. Hold the wire in the right hand till you see that the piece of agaric gives no more smoke, but is become quite a red hot coal. Then thrust it immediately in the bottle, more than half its depth, and keep it there till it is consumed. The coal of the agaric will increase in heat so as to set fire to the end of the wire. The flame will slowly run up, and the melted metal will now and then fall to the bottom of the glass, and will crack it, if you leave water in the bottle. You will be highly delighted with the experiment. My bottles for that purpose have a metallic bottom. You have only to send an empty bottle of flint glass, with a good cork stopper upon it, to M. Sigau de la Fond, who lives in the Rue St. Jaques, in the neighbourhood of M. le Beguer. He has always a good deal of dephlogisticated air ready, and will be glad to let you have as much as you please. You must remind him not to leave more water in the bottle, than is sufficient to keep the cork moist, for the motion of water with this air spoils the air.

J. INGENHOUSz.

FROM EDWARD NAIRNE TO B. FRANKLIN.

A Hygrometer on a New Construction.M. De Luc's

Hygrometer.

DEAR SIR,

London, 2 December, 1783.

I received your favors. The book and prints, which Mr. Argand was so obliging as to deliver, I have since sent to Sir Joseph Banks, agreeably to your request. I am very much obliged to you for your observations on the alteration of the wood of the box belonging to the magnets. Since I received your favor, I have been endeavouring to make as simple an instrument as possible for a hygrometer, a drawing of which is annexed.

LL*

In Fig. 1, A is a piece of wood about twelve inches

long and two inches broad, cut crosswise the grain of

the wood, which slides freely between the two pieces of wood, B, B, forming grooves for it. C is a screw for adjusting the piece of wood, A, so that the index may point to the proper division when first made. In Fig. 2, a is a slit to admit the pin e to move freely, which pin, by being fast in the piece of wood, A, moves with it as it shortens or lengthens, and, by pressing against the short end of the index, D, causes it to move up or down according as the weather is moist or dry, which is shown on the divided arch, at the upper end of the instrument.*

If you should at your leisure consider it, and if you find that it is not adequate to the purpose wanted, I should esteem it a great favor if you would inform me of it, or if any alterations or additions can be added to it.t

I was the day before yesterday at Windsor, where M. De Luc showed me a hydrometer. It was made of a thin piece of whalebone, about nine inches long, and was kept straight by a line fastened to it going over a pulley, the other end of which line was fastened to a spiral spring. He observed, that it was the only substance he had ever met with, that would always return to the same length when soaked in water. It altered in its length about one inch from extreme moisture to extreme dryness.

I sent you some time ago the account of shortening wire by lightning, which I hope you have received.

I am, dear Sir, your most obliged, &c.

EDWARD NAirne.

*It is to be observed, that Fig. 1. is the back part of the instrument, or a thin box upon which is placed Fig. 2, as a cover, being the face of the instrument. - EDITOR.

See the letter, containing directions for making this hygrometer above, p. 426.