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coat might, in the progress of the experiment, be longer melting. They should therefore be kept so long in the wax, as to be all well and equally heated. Perhaps you may thus find the progress of heat in the silver quicker and greater. I think, also, that if the hot oil in which you dipped the ends was not stagnant, but in motion, the experiment would be more complete, because the wire which quickest diminishes the heat of the oil next to it, finds soonest the difficulty of getting more heat from the oil farther distant, which depends on the nature of the oil as a conductor of heat, that which is already cooled interfering between the hotter oil and the wire. In reversing the experiment also, to try which of the metals cools fastest, I think the wires should be dipped in running cold water; for when stagnant, the hot wires, by communicating heat to the water that is near them, will make it less capable of receiving more heat; and as the metals which communicate their heat most freely and readily will soonest warm the water round them, the operation of such metals may therefore soonest stop,-not because they naturally longer withhold their heat, but because the water near them is not in a state to receive it. I do not know that these hints are founded; I suggest them only as meriting a little consideration. Every one is surprised that the progress of the heat seems to have no connexion with the gravity or the levity of the metals. B. FRANKLIN.

AN ACCOUNT OF TOADS

FOUND ENCLOSED IN THE SOLID OF A STONE QUARRY.

Ar Passy, near Paris, April 6, 1782, being with M. De Chaumont, viewing his quarry, he mentioned to me, that the workmen had found a living toad shut up in the stone. On questioning one of them, he told us they had found four in different cells which had no communication: that they were very lively and active when set at liberty: that there was in each cell some loose, soft, yellowish earth, which appeared to be very moist. We asked, if he could show us the parts of the stone that formed the cells? He said no; for they were thrown among the rest of what was dug out, and he knew not where to find them. We asked, if there appeared any opening by which the animal could enter? He said, no, not the least. We asked if, in the course of his business as a laborer in quarries, he had often met with the like? He said, never before.

VOL. III.

3 L

We asked, if he could show us the toads? He said, he had thrown two of them up on a higher part of the quarry, but knew not what became of the others. He then came up to the place where he had thrown the two, and finding them, he took them by the foot, and threw them up to us, upon the ground where we stood. One of them was quite dead and appeared very lean: the other was plump and still living. The part of the rock where they were found, is at least 15 feet below its surface, and is a kind of limestone. A part of it is filled with ancient sea shells, and other marine substances. If these animals have remained in this confinement since the formation of the rock, they are probably some thousands of years old. We have put them in spirits of wine, to preserve their bodies a little longer. The workmen have promised to call us if they meet with any more, that we may examine their situation. Before a suitable bottle could be found to receive them, that which was living when we first had them, appeared to be quite dead and motionless; but being in the bottle, and the spirits poured over them, he flounced about in it very vigorously for two or three minutes, and then expired.

It is observed that animals who perspire but little, can live long without food; such as tortoises, whose flesh is covered with a thick shell, and snakes, who are covered with scales, which are of so close a substance as scarcely to admit the passage of perspirable matter through them. Animals that have open pores all over the surface of their bodies, and live in air which takes off continually the perspirable part of their substance, naturally require a continual supply of food to maintain their bulk. Toads shut up in solid stone, which prevents their losing any thing of their substance, may perhaps for that reason need no supply; and being guarded against all accidents, and all the inclemencies of the air and changes of the seasons, are, it seems, subject to no diseases, and become as it were immortal. B. F.

[The following copy of a letter from Sir John Pringle to Mr. A. Small, was annexed to the above account, in Dr. F.'s papers.]

TO MR. SMALL.

SIR,

Minorca, April 25, 1780.

Last year I had the honor to inform you, that two of those large moths called Muskitoe Hawks, which appear about September, and disappear about the beginning of December, lived 71 days after I had cut their heads off with a pair of scissars.

"

The last autumn I made the same experiment upon several, keeping them under separate glasses, in a closet, where there was no fire. The most of them lived different periods, from 3, to 60 and 70 days. Those which exceeded that number of days, were four, viz. one from the 30th of October to the 21st of January, 83 days; one from the 12th of December to the 21st of April, 131 days; and one from the 24th of October to the 15th of April, 174 days. As they are very active, and covered with a sort of plumage, which makes it difficult to cut their heads off, without bruising or otherwise injuring the body, I imagine that may partly be the reason of their living different periods; and if, after the operation, any glutinous liquor proceeded from the body, that moth would die soon. I put several under glasses, without cutting off their heads, none of which lived many days. I am, sir, with great esteem, your most obedient and most humble servant,

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QUERIES ON ELECTRICITY,

FROM DR. INGENHAUSZ; WITH ANSWERS, BY DR. FRANKLIN.

Question 1.

If the electrical fluid is truly accumulated on the inside of a Leyden phial, and expelled in the same proportion from the other side, why are the particles of glass not all thrown outwards, when the phial being overcharged, breaks or is perforated by a spontaneous explosion?

Answer.

By the circumstances that have appeared to me, in all the jars that I have seen perforated at the time of their explosion, I have imagined that the charge did not pass by those perforations. Several single jars that have broke while I was charging them, have shown, besides the perforation in the body, a trace on both sides of the neck, where the polish of the glass was taken off the breadth of a straw; which proved that great part at least of the charge, probably all, had passed over that trace. I was once present at the discharge of a battery containing thirty jars, of which eight were perforated and spoilt at the time of the discharge, yet the effect of the charge on the bodies upon which it was intended to operate, did not appear to be diminished. Another time I was present when twelve out of twenty jars were broken at the time of the discharge, yet the effect of the charge which passed in the regular circuit, was the same as it would have been if they had remained whole. Were those perforations an

effect of the charge within the jar forcing itself through the glass to get at the outside, other difficulties would arise, and demand explanation. 1. How it happens that in eight bottles, and in twelve the strength to bear a strong charge should be so equal, that no one of them would break before the rest, and thereby save his fellows; but all should burst at the same instant? 2. How it happens that they bear the force of the great charge till the instant that an easier means of discharge is offered them, which they make use of, and yet the fluid breaks through at the same time?

My conjecture is, that there has been in the place where the rupture happens, some defect in the glass, some grain of sand perhaps, or some little bubble in the substance nearly void, where during the charging of the jar, the electric fluid forced in and confined till the pressure is suddenly taken off by the discharge, when not being able to escape so quickly, it bursts its way out by its elastic force. Hence all the ruptures happen nearly at the same instant with the regular discharge, though really a little posterior, not being themselves discharges, but the effects of a discharge which passed in another channel.

Question 2.

When a strong explosion is directed through a pack of cards or a book, having a piece of tin foil between several of its leaves, the electrical flash makes an impression in some of those metallic leaves, by which it seems as if the direction of the electric explosion had gone from the outside towards the inside, when on the other metallic leaves, the impression is in such a direction, that it indicates the current of electrical fire to have made its way from the inside of the phial towards the outside; so that it appears to some electricians, that in the time of the explosion of an electrical phial, two streams of electrical fire rush at the same time from both surfaces, and meet or cross one another.

Answer.

These impressions are not effects of a moving body, striking with force in the direction of its motion; they are made by the burrs rising in the neighboring perforated cards, which rise accidentally sometimes on one side of a card, sometimes on the other, in consequence of certain circumstances in the form of their substances or situations. In a single card, supported without touching others, while perforated by the passing fluid, the burr generally rises on both sides, as I once showed to Mr. Symmer at his house. I imagine that the hole is made

by a fine thread of electric fluid first passing, and augmented to a bigger thread at the time of the explosion, which obliging the parts of a card to recede every way, condenses a part within the substance, and forces a part out on each side, because there is least resistance.

Question 3.

When a flash of lightning happens to hit a flat piece of metal, the metal has sometimes been pierced with several holes, whose edges were turned some the one way and some the other, so that it has appeared to some philosophers that several streams of electrical fire had rushed in one way, and some the opposite way. Such an effect of lightning has been published lately by Father Barletti.

Answer.

This will be answered in my remarks on Mr. Barletti's book; which remarks, when finished, I will send you.

Question 4.

Though from the very charging of the Leyden phial, it seems clear, that the electrical fluid does in reality not pervade the substance of glass, yet it is still difficult to conceive how such a subtile fluid may be forced out from one side of a very thick pane of glass, by a similar quantity of electrical fire thrown upon the other surface, and yet that it does not pass through any substance of glass, however thin, without breaking it. Is there some other fact or illustration besides those to be found in your public writings, by which it may be made more obvious to our understanding, that electrical fire does not enter at all the very substance of glass, and yet may force from the opposite surface an equal quantity; or that it really enters the pores of the glass without breaking it? Is there any comparative illustration or example in nature, by which it may be made clear, that a fluid thrown upon one surface of any body, may force out the same fluid from the other surface without passing through the substance?

Answer.

That the electric fluid, by its repulsive nature, is capable of forcing portions of the same fluid out of bodies without entering them itself, appears from this experiment. Approach an isolated body with a rubbed tube of glass; the side next the tube will then be electrised negatively, the opposite positively. If

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