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"On Thursday, the 9th of November, I had an opportunity of observing a transit of Mercury. I had carefully adjusted my clock to the apparent time, by correspondent altitudes of the Sun, taken with the quadrant for several days before, and with the same reflecting telescope as I used for the transit of Venus.* I first perceived the little planet making an impression on the sun's limb at 2 52' 41"; and he appeared wholly within at 53′ 58′′ apparent time. The sun set before the planet reached the middle of his course; and for a considerable time before sunset, it was so cloudy, that the planet could not be discerned. So that I made no observations of consequence, except that of the beginning, at which time the sun was perfectly clear. This transit completes three periods of forty-six years, since the first observation of Gassendi at Paris, in 1631."

I am, Sir, with great esteem,

Your most obedient servant,

B. FRANKLIN.

TO MICHAEL HILLEGAS.

Respecting covering Houses with Copper.

DEAR SIR,

London, 17 March, 1770.

I received your favor of November 25th, and have made inquiries, as you desired, concerning the copper covering of houses. It has been used here in a few instances only, and the practice does not seem to gain ground. The copper is about the thickness of a common playing-card; and, though a dearer metal than *See Philosophical Transactions, Vol. LIX. p. 352. VOL. VI.

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lead, I am told, that, as less weight serves, on account of its being so much thinner, and as slighter woodwork in the roof is sufficient to support it, the roof is not dearer on the whole, than one covered with lead.

It is said, that hail and rain make a disagreeable drumming noise on copper; but this I suppose is rather fancy; for the plates being fastened on the rafters must, in a great measure, deaden such sound. The first cost, whatever it is, will be all, as a copper covering must last for ages; and, when the house decays, the plates will still have intrinsic worth. In Russia, I am informed, many houses are covered with plates of iron tinned, such as our tin pots and other vases are made of, laid on over the edges of one another like tiles; and which, it is said, last very long, the tin preserving the iron from much decay by rusting. In France and the Low Countries, I have seen many spouts or pipes for conveying the water down from the roofs of houses, made of the same kind of tin plates soldered together; and they seem to stand very well.

With sincere regard, I am
Yours, &c.

B. FRANKLIN.

SIR,

FROM JOHN EWING TO B. FRANKLIN.

Philadelphia, 14 June, 1770.

I received your very agreeable letter, in which you acknowledge the receipt of our observations of the transit of Venus. I herewith send you a few copies of them, as they are printed in our Transactions, and I suppose in a more perfect form than that in which they were sent before, as that was done in a hurry, and I

have not a copy of what I sent. If what you received before is not printed in the Philosophical Transactions, please to request Mr. Maskelyne to insert them as they are now sent, unless he should think it better to abridge or alter them, as to their dress or form, which he has full liberty to do, as he is much better acquainted with publications of this kind than I can be supposed to be.

I mentioned to our Society your proposal to purchase the Transactions of the learned societies in Europe, and they have taken the matter under their consideration. They approved of your reasoning on the subject, when I read it to them; and nothing will prevent their coming into the resolution, if their poverty does not.

I hope, that before this time Mr. Maskelyne has given you an estimate of the expense and apparatus necessary for erecting an observatory here, where we are blessed with so happy a serenity of air for astronomical observations. I have not yet mentioned this matter to our Society, but wait until I hear farther from you; and would still choose, that, when proposed, it should come from you and the Astronomer Royal, to whose judgment our Society pay the greatest respect in these matters.

Please to accept of my hearty thanks for the perusal of your last volume of the Philosophical Transactions. I shall deliver it safely to Mrs. Franklin.

When the observations of the transit of Venus come to hand from the East Indies, the North of Europe, or from South America, I shall be much obliged to you for a copy of them, as I am anxious to know how they correspond with ours.

I am, Sir, your most obedient and very humble

servant,

JOHN EWING.

P. S. Please to deliver one of the copies with my compliments to the Astronomer Royal, the Reverend Mr. Maskelyne.

TO SAMUEL RHOADS.

On securing Houses from Fire.

DEAR FRIEND,

London, 26 June, 1770.

It is a long time since I had the pleasure of hearing from you directly. Mrs. Franklin has indeed now and then acquainted me of your welfare, which I am always glad to hear of. It is, I fear, partly, if not altogether my fault, that our correspondence has not been regu larly continued. One thing I am sure of, that it has been from no want of regard on either side, but rather from too much business, and avocations of various kinds, and my having little of importance to communicate.

One of our good citizens, Mr. Hillegas, anxious for the future safety of our town, wrote to me some time since, desiring I would inquire concerning the covering of our houses here with copper. I sent him the best information I could then obtain, but have since received the enclosed from an ingenious friend, who is what they call here a civil engineer. I should be glad you would peruse it, think of the matter a little and give me your sentiments of it. When you have done with the paper, please to give it to Mr. Hillegas. I am told by Lord Despencer, who has covered a long piazza, or gallery, with copper, that the expense is charged in this account too high; for his cost but one shilling and ten pence per foot, all charges included. I suppose his copper

must have been thinner. And, indeed, it is so strong a metal, that I think it may well be used very thin.

It appears to me of great importance, to build our dwellinghouses, if we can, in a manner more secure from danger by fire. We scarcely ever hear of fire in Paris. When I was there I took particular notice of the construction of their houses, and I did not see how one of them could well be burnt. The roofs are slate or tile, the walls are stone, the walls generally lined with stucco or plaster, instead of wainscot, the floors of stucco, or of six square tiles painted brown, or of flag stone, or of marble; if any floors were of wood, it was of oak wood, which is not so inflammable as pine. Carpets prevent the coldness of stone or brick floors offending the feet in winter, and the noise of treading on such floors overhead, is less inconvenient than on boards.

The stairs too, at Paris, are either stone or brick, with only a wooden edge or corner for the step; so that on the whole, though the Parisians commonly burn wood in their chimneys, a more dangerous kind of fuel than that used here, yet their houses escape extremely well, as there is little in a room that can be consumed by fire except the furniture; whereas in London, perhaps scarcely a year passes in which half a million of property and many lives are not lost by this destructive element. Of late, indeed, they begin here to leave off wainscoting their rooms, and instead of it cover the walls with stucco, often formed into pannels like wainscot, which, being painted, is very strong and warm. Stone staircases too, with iron rails, grow more and more into fashion here; but stone steps cannot, in some circumstances, be fixed; and there, methinks, oak is safer than pine; and I assure you, that in many genteel houses here, both old and new, the stairs and floors are oak, and look extremely well. Perhaps solid oak

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