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tation that the sound of such blessed bells would drive away those storms, and secure our buildings from the stroke of lightning; and during so long a period, it has not been found by experience, that places within the reach of such blessed sound are safer than others where it is never heard ; but that, on the contrary, the lightning seems to strike steeples of choice, and that at the very time the bells are ringing ; * yet still they continue to bless the new bells, and jangle the old ones whenever it thunders. One would think it was now time to try some other trick; and ours is recommended (whatever this able philosopher may have been told to the contrary) by more than twelve years' experience, wherein, among the great number of houses furnished with iron rods in North America, not one so guarded has been materially hurt with lightning, and several have been evidently preserved by their means; while a number of houses, churches, barns, ships, &c. in different places, unprovided with rods, have been struck and greatly damaged, demolished, or burnt. Probably the vestries of our English churches are not generally well acquainted with these facts; otherwise, since as good Protestants they have no faith in the blessing of bells, they would be less excusable in not providing this other

inimici, fragor grandinum, procella turbinum, impetus tempestatum, temperentur infesta tonitrua," &c.

“Omnipotens, sempiterne Deus, &c., ..... ut ante sonitum ejus effugentur ignita jacula inimici, percussio fulminum, impetus lapidum, læsio tempestatum,” &c.

“En 1718, M. Deslandes fit savoir à l'Académie Royale des Sciences, que la nuit du 14 ou 15 d'Avril de la même année, le tonnerre étoit tombé sur vingt-quatre églises, depuis Landernau jusqu'à Saint-Polde-Léon en Bretagne ; que ces églises étoient précisément celles ou l'on sonnoit, et que la foudre avoit épargné celles où l'on ne sonnoit pas; que dans celle de Gouisnon, qui fut entièrement ruinée, le tonnerre tua deux personnes de quatre qui sonnoient,” &c.Histoire de l'Académie Royale des Sciences, 1719.

security for their respective churches, and for the good people that may happen to be assembled in them during a tempest, especially as those buildings, from their greater height, are more exposed to the stroke of lightning than our common dwellings.

I have nothing new in the philosophical way to communicate to you, except what follows. When I was last year in Germany, I met with a singular kind of glass, being a tube about eight inches long, half an inch in diameter, with a hollow ball of near an inch diameter at one end, and one of an inch and half at the other, hermetically sealed, and half filled with water. If one end is held in the hand, and the other a little elevated above the level, a constant succession of large bubbles proceeds from the end in the hand to the other end, making an appearance that puzzled me much, till I found that the space not filled with water was also free from air, and either filled with a subtile, invisible vapor continually rising from the water, and extremely rarefiable by the least heat at one end, and condensable again by the least coolness at the other; or it is the very fluid of fire itself, which parting from the hand pervades the glass, and by its expansive force depresses the water till it can pass between it and the glass, and escape to the other end, where it gets through the glass again into the air. I am rather inclined to the first opinion, but doubtful between the two.

An ingenious artist here, Mr. Nairne, mathematical instrument-maker, has made a number of them from mine, and improved them; for his are much more sensible than those I brought from Germany. I bored a very small hole through the wainscot in the seat of my window, through which a little cold air constantly entered, while the air in the room was kept warmer by fires daily made in it, being winter time. I placed one of his glasses, with the elevated end against this hole; and the bubbles from the other end, which was in a warmer situation, were continually passing day and night, to the no small surprise of even philosophical spectators. Each bubble discharged is larger than that from which it proceeds, and yet that is not diminished; and by adding itself to the bubble at the other end, that bubble is not increased, which seems very paradoxical. When the balls at each end are made large, and the connecting tube very small, and bent at right angles, so that the balls, instead of being at the ends, are brought on the side of the tube, and the tube is held so as that the balls are above it, the water will be depressed in that which is held in the hand, and rise in the other as a jet or fountain; when it is all in the other, it begins to boil, as it were, by the vapor passing up through it; and the instant it begins to boil, a sudden coldness is felt in the ball held; a curious experiment this, first observed and shown me by Mr. Nairne. There is something in it similar to the old observation, I think mentioned by Aristotle, that the bottom of a boiling pot is not warm; and perhaps it may help to explain that fact; if indeed it be a fact. When the water stands at an equal height in both these balls, and all at rest, if you wet one of the balls by means of a feather dipped in spirit, though that spirit is of the same temperament as to heat and cold with the water in the glasses, yet the cold occasioned by the evaporation of the spirit from the wetted ball will so condense the vapor over the water contained in that ball, as that the water of the other ball will be pressed up into it, followed by a succession of bubbles, till the spirit is all dried away. Perhaps the observations on these little instruments may suggest and be WOL. W. 54 JJ*


applied to some beneficial uses. It has been thought, that water reduced to vapor by heat was rarefied only fourteen thousand times, and on this principle our engines for raising water by fire are said to be constructed; but, if the vapor so much rarefied from water is capable of being itself still farther rarefied to a boundless degree, by the application of heat to the vessels or parts of vessels containing the vapor (as at first it is applied to those containing the water), perhaps a much greater power may be obtained, with little additional expense. Possibly too, the power of easily moving water from one end to the other of a movable beam (suspended in the middle like a scale-beam) by a small degree of heat, may be applied advantageously to some other mechanical purposes.

The magic square and circle, I am told, have occasioned a good deal of puzzling among the mathematicians here; but no one has desired me to show him my method of disposing the numbers. It seems they wish rather to investigate it themselves. When I have the pleasure of seeing you, I will communicate it. With singular esteem and respect, I am, dear Sir, Your most obedient humble servant,



On some Electrical Experiments made with Charcoal.

Philadelphia, 13 October, 1770. THE conducting quality of some sorts of charcoal is indeed very remarkable. I have found oak, beech, and maple to conduct very well; but tried several pieces of pine coal 'without finding one that would conduct at all; perhaps they were made in a fire not hot enough, or not continued in it long enough. A strong line, drawn on paper with a black lead pencil, will conduct an electrical shock pretty readily ; but this, perhaps, may not be new to you. · On the 12th of last July, three houses in this city, and a sloop at one of the wharfs, were, in less than an hour's time, all struck with lightning. The sloop, with two of the houses, was considerably damaged; the other was the dwellinghouse of Mr. Joseph Moulde, in Lombard Street, which was provided with a round iron conductor, half an inch thick, its several lengths screwed together, so as to make very good joints, and the lower end five or six feet under ground; the lightning, leaving every thing else, pursued its way through that, melted off six inches and a half of the slenderest part of a brass wire fixed on the top, and did no further damage, within doors or without Captain Falconer, who brings you this, was in the house at the time of the stroke, and says it was an astonishing loud one.




On the Security of the Powder Magazines at Purfleet.

Craven Street, 29 May, 1772.


Having visited yesterday, as you desired, the powder magazines at Purfleet, in order to see how they may be protected against danger from lightning, I think,

* This letter is here printed in a translation from the French, as contained in M. Dubourg's edition of the author's writings, (Tom. I. p. 280.) - EDITOR.

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