a ship; so I suppose it to be only the drops thrown off from the spout, by the centrifugal force (as the birds were at Hatfield), when they had been carried so high as to be above, or to be too strongly centrifugal for, the pressure of the concurring winds surrounding it. And, indeed, I believe there can be no other kind of salt rain; for it has pleased the goodness of God so to order it, that the particles of air will not attract the particles of salt, though they strongly attract water.

Hence, though all metals, even gold, may be united with air, and rendered volatile, salt remains fixed in the fire, and no heat can force it up to any considerable height, or oblige the air to hold it. Hence, when salt rises, as it will a little way, into air with water, there is instantly a separation made; the particles of water adhere to the air, and the particles of salt fall down again, as if repelled and forced off from the water by some power in the air; or, as some metals, dissolved in a proper menstruum, will quit the solvent when other matter approaches, and adhere to that, so the water quits the salt, and embraces the air; but air will not embrace the salt, and quit the water, otherwise our rains would indeed be salt, and every tree and plant on the face of the earth be destroyed, with all the animals that depend on them for subsistence. He who hath proportioned and given proper qualities to all things, was not unmindful of this. Let us adore HIM with praise and thanksgiving!

By some accounts of seamen, it seems the column of water, W W, sometimes falls suddenly; and if it be, as some say, fifteen or twenty yards diameter, it must fall with great force, and they may well fear for their ships. By one account, in the Transactions, of a spout that fell at Colne in Lancashire, one would think the column is sometimes lifted off from the water, and

carried over land, and there let fall in a body; but this, I suppose, happens rarely.

Stuart describes his spouts as appearing no bigger than a mast, and sometimes less; but they were seen at a league and a half distance.

I think I formerly read in Dampier, or some other voyager, that a spout, in its progressive motion, went over a ship becalmed on the coast of Guinea, and first threw her down on one side, carrying away her foremast, then suddenly whipped her up, and threw her down on the other side, carrying away her mizen-mast, and the whole was over in an instant. I suppose the first mischief was done by the fore side of the whirl, the latter by the hinder side, their motion being contrary.

I suppose a whirlwind, or spout, may be stationary, when the concurring winds are equal; but if unequal, the whirl acquires a progressive motion, in the direction of the strongest pressure.

When the wind that gives the progressive motion. becomes stronger below than above, or above than below, the spout will be bent, and, the cause ceasing, straighten again.

Your queries, towards the end of your paper, appear judicious, and worth considering. At present I am not furnished with facts sufficient to make any pertinent answer to them; and this paper has already a sufficient quantity of conjecture.

Your manner of accommodating the accounts to your hypothesis of descending spouts is, I own, ingenious, and perhaps that hypothesis may be true. I will consider it farther; but, as yet, I am not satisfied with it, though hereafter I may be.

Here you have my method of accounting for the principal phenomena, which I submit to your candid

examination.

And, as I now seem to have almost written a book, instead of a letter, you will think it high time I should conclude; which I beg leave to do, with assuring you, that I am, Sir, &c.

B. FRANKLIN.

TO JAMES BOWDOIN.

Relating to the Transit of Mercury in 1753.

DEAR SIR,

Philadelphia, 28 February, 1753.

The enclosed is a copy of a letter and some papers I received lately from a friend, of which I have struck off fifty copies by the press, to distribute among my ingenious acquaintance in North America, hoping some of them will make the observations proposed. The improvement of geography and astronomy is the common concern of all polite nations, and, I trust, our country will not miss the opportunity of sharing in the honor to be got on this occasion. The French originals are despatched by express overland to Quebec. I doubt not but you will do what may lie in your power, to promote the making these observations in New England, and that we may not be excelled by the American French, either in diligence or accuracy. We have here a three-foot reflecting telescope, and other proper instruments; and intend to observe at our Academy, if the weather permit. You will see, by our Almanac, that we have had this transit under consideration before the arrival of these French letters.*

The paper alluded to, of which fifty copies were struck off for distribution, was entitled, "Letters relating to a Transit of Mercury over the

Dr. Colden's book was printed in England last summer, but not to be published till the meeting of Parliament. I have one copy, however, which I purpose shortly to send you.

With great esteem and respect, I am, Sir,

Your most humble servant,

I received your favor of March 26th, and thank you for communicating to me the very ingenious letter from your friend, Mr. Todd, with whom, if it may be agreeable to him, I would gladly entertain a correspondence. I shall consider his objections till next post.

I thank you for your hint concerning the word adhesion, which should be defined. When I speak of particles of water adhering to particles of air, I mean not

Sun, which is to happen May 6th, 1753." It consisted of four large folio pages, and contained all the information necessary to enable a person little skilled in astronomy to observe the transit. A manuscript drawing was also attached to each copy, showing the line in which Mercury would pass over the sun's disc.

The translation of these papers was made in New York under the direction of Mr. James Alexander, who sent them to Franklin. The French astronomers were desirous, that observations of the transit should be taken at Quebec. M. de Lisle, of the Academy of Sciences, drew up a memorial containing instructions for the purpose. This memorial, with letters from M. La Gallissonière, dated at Paris, October 10th, 1752, was sent unsealed to the governor of New York, with a request that they might be forwarded over land to Quebec. The governor put the papers into the hands of Mr. Alexander, who caused a translation to be made.