sufficient quantity of these particles to cover a considerable portion of the surface of the sea; which particles, being differently dispersed, might account for the dif ferent degrees of light in the appearance above mentioned. But this account seems liable to this obvious objection, that as putrid fish, &c. make a luminous appearance without being moved or disturbed, it might be expected that the supposed putrid particles on the surface of the sea should always appear luminous, where there is not a greater light; and, consequently, that the whole surface of the sea, covered with those particles, should always in dark nights, appear luminous, without being disturbed. But this is not fact.

Among the rest, I threw out my conjecture, that the said appearance might be caused by a great number of little animals, floating on the surface of the sea, which, on being disturbed, might, by expanding their fins, or otherwise moving themselves, expose such a part of their bodies as exhibits a luminous appearance, somewhat in the manner of a glow-worm or fire-fly that these animals may be more numerous in some places than others; and, therefore, that the appearance above mentioned, being fainter and stronger in different places, might be owing to that; that certain circumstances of weather, &c. might invite them to the surface, on which in a calm they might sport themselves and glow; or in storms, being forced up, make the same appearance.

There is no difficulty in conceiving that the sea may be stocked with animalcula for this purpose, as we find all nature crowded with life. But it seems difficult to conceive that such small portions of matter, even if they were wholly luminous, should affect our sight. much more so, when it is supposed that only a part of them is luminous. But, if we consider some other

appearances, we may find the same difficulty to conceive of them; and yet we know they take place. For instance, the flame of a candle, which, it is said, may be seen four miles round. The light which fills this circle of eight miles diameter was contained, when it first left the candle, within a circle of half an inch diameter. If the density of light, in these circumstances, be as those circles to each other, that is, as the squares of their diameters, the candle-light, when come to the eye, will be 1,027,709,337,600 times rarer than when it quitted the half-inch circle. Now the aperture of the eye, through which the light passes, does not exceed one tenth of an inch diameter, and the portion of the lesser circle, which corresponds to this small portion of the greater circle, must be proportionably, that is, 1,027,709,337,600 less than one tenth of an inch; and yet this infinitely small point (if you will allow the expression) affords light enough to make it visible four miles; or, rather, affords light sufficient to affect the sight at that distance.

The smallness of the animalcula is no objection, then, to this conjecture; for, supposing them to be ten thousand times less than the minimum visibile, they may, notwithstanding, emit light enough to affect the eyes, and so to cause the luminous appearance aforesaid. This conjecture I send you for want of something

better.

I am, with the greatest esteem, &c.

JAMES BOWDOIN.*

See Dr. Franklin's remarks on this letter, in his answer, dated De

cember 13th, 1753, in Vol. V. p. 337.- EDITOR.

FROM M. DALIBARD TO B. FRANKLIN.

TRANSLATION.

Intelligence on Philosophical Subjects.

MY DEAR FRIEND,

Paris, 31 March, 1754.

I received on the 15th of January last, your obliging letter of October 28th. I did not reply to it immediately, because I thought it best to wait for what you were to send me by the next vessel, which you informed me would sail eight or ten days later. I have waited till this time, without having received any thing but a small parcel of seeds, and a very kind letter from our respected friend, Mr. Bartram. Our worthy correspondent, Mr. Collinson, forwarded it to me by a mutual friend, who furnishes me with another opportunity of sending letters to England. It is only two days since I received Mr. Bartram's packet, and I beg you will have the kindness to send him my answer.

I learned, a short time before I received your last letter, that the vessel, on board which was the parcel of books which I sent to Mr. Collinson for you, had been lost at the mouth of the Thames. I regretted extremely this loss, which it is not possible for me fully to repair, as there were some books among them, which I had received from Germany, and which I cannot obtain again here. I intend to send you, by the first opportunity I can find direct to London, the books for which you asked me, namely, the four volumes of Buffon's Natural History, two copies of your Letters, and the Maps of North and South America by Delisle and Buache. To these I shall add two copies of my Flora Parisiensis; and if the translation, which I am causing to be made, of a work on Electricity by M. Beccaria,

presented to me by the author, is finished, I shall send you the original Italian.

The hope of soon receiving what you announced .o me in your letter of October 28th, has caused me to delay the new edition of your Letters on Electricity till this time. Besides this, urgent business of various kinds has so occupied my time during the whole of the last winter, that I have been able to devote but few moments to philosophical studies. I have regretted, and still regret this the more, as we have had in this country the finest weather for electrical experiments. I have not been able to procure a sulphur globe, such as I proposed to have, because I have not had time to be present while it was making. It is owing to this same want of time, that the attempt to make my electrometer has not yet proved successful. But I have not given up the one or the other. I hope to give my attention to them shortly, as soon as I shall be somewhat relieved from the pressure of business; and I shall again devote myself to electricity, which still seems to me worthy of the most diligent study.

All our philosophical friends, Messrs. Buffon, Fonferrière, Marty, &c., charge me to make you their best compliments, and M. Dubourg also. We are all waiting with the greatest eagerness to hear from you. I beg that you will let me have letters as soon and often as possible. Your name is venerated in this country as it deserves to be. There are but few electricians, like the Abbé Nollet, whose jealousy is excited by the honor your discoveries have obtained.

With great respect and esteem,
I am, &c.

DALIBARD

FROM CADWALLADER COLDEN TO B. FRANKLIN.

Water-Spouts. Wind generated by Fermentation. —

Winds blowing in contrary Directions.

READ AT THE ROYAL SOCIETY, DECEMBER 6TH, 1756.

2 April, 1754.

ANY knowledge I have of the winds, and other changes which happen in the atmosphere, is so very defective, that it does not deserve the name; neither have I received any satisfaction from the attempts of others on this subject. It deserves then your thoughts, as a subject in which you may distinguish yourself, and be useful.

Your notion of some things conducting heat or cold better than others pleases me, and I wish you may pursue the scent. If I remember right, Dr. Boerhaave, in his Chemistry, thinks that heat is propagated by the vibration of a subtile, elastic fluid, dispersed through the atmosphere and through all bodies. Sir Isaac Newton says, there are many phenomena to prove the existence of such a fluid; and this opinion has my assent to it. I shall only observe, that it is essentially different from that which I call ether; for ether, properly speaking, is neither a fluid nor elastic; its power consists in reacting any action communicated to it, with the same force it receives the action.

I long to see your explication of water-spouts; but I must tell you beforehand, that it will not be easy for you to convince me, that the principal phenomena were not occasioned by a stream of wind issuing with great force; my eyes and ears both concurring to give me this sentiment, I could have no more evidence than to feel the effects, which I had no inclination to do.