the end of the siphon, the water issued at both glass tubes, with equal force, and on only half stopping the end of the siphon, it did the same. I imagine the sudden bending of the siphon gives such a resistance to the stream, as to occasion its issuing out of the glass tube c. But I intend to try a farther experiment, of which I shall give you an account.

I am now determined to publish an American Philosophical Miscellany, monthly or quarterly. I shall begin with next January, and proceed as I find encouragement and assistance. As I purpose to take the compiling wholly upon myself, the reputation of no gentleman or society will be affected by what I insert of another's; and that perhaps will make them more free to communicate. Their names shall be published or concealed, as they think proper, and care taken to do exact justice to matters of invention, &c. I shall be glad of your advice in any particulars that occurred to you in thinking of this scheme; for, as you first proposed it to me, I doubt not but you have well considered it.*

I have not the original of Dr. Mitchell's tract on the Yellow Fever. Mine is a copy I had taken, with his

leave, when here.

for you.

Mr. Evans will make a copy of it

I hope it will be confirmed by future experiment, that the yaws are to be cured by tar-water. The case you relate to Dr. Mitchell gives great hopes of it, and should

* It does not appear that this scheme was ever carried into execution. EDITOR.

-

† Dr. John Mitchell was a learned physician and botanist, and Fellow of the Royal Society. He was a native of England, but came over and established himself in Virginia. Dr. Miller says, that "he wrote ably on the yellow fever, as it appeared in Virginia in 1742; and that his instructive manuscripts on this subject fell into the hands of Dr. Franklin, by whom they were communicated to Dr. Rush." - MILLER'S Retrospect, Vol. I. p. 318. — Editor.

be published, to induce people to make trials. For, though it should not always succeed, I suppose there is no danger of its doing any harm.

As to your pieces on Fluxions and the different species of matter, it is not owing to reservedness that I have not yet sent you my thoughts; but because I cannot please myself with them, having had no leisure yet to digest them. If I was clear, that you are anywhere mistaken, I would tell you so, and give my reasons with all freedom, as believing nothing I could do would be more obliging to you. I am persuaded you think, as I do, that he who removes a prejudice, or an error, from our minds, contributes to their beauty, as he would do to that of our faces, who should clear them of a wart or a wen.

I have a friend gone to New York with a view of settling there, if he can meet with encouragement. It is Dr. John Bard, whom I esteem an ingenious physician and surgeon, and a discreet, worthy, and honest man. If, upon conversation with him, you find this character just, I doubt not but you will afford him your advice and countenance, which will be of great service to him in a place where he is entirely a stranger, and very much oblige, Sir,

Your most humble servant,

*

B. FRANKLIN.

P. S. I shall forward your letter to Dr. Mitchell. Thank you for leaving it open for my perusal.

* This introduction was the origin of a long and intimate friendship between Dr. Bard and Mr. Colden. For his professional skill, his active public spirit, and his private worth, no man of his time was more highly valued than Dr. John Bard. His talents and his virtues were inherited by his son, Dr. Samuel Bard, of whom a very interesting memoir has been published by Professor M Vickar. In that work, speaking of Dr. John Bard, the father, Professor Mc Vickar says; "He was a man whe

TO CADWALLADER COLDEN.

Conjecture as to the Cause why Ships in crossing the Atlantic have longer Passages in sailing westward than in sailing eastward.

SIR,

[Date uncertain.]

I received yours, with others enclosed for Mr. Bartram and Mr. Armit, to which I suppose the enclosed are answers. The persons who brought yours said he would call for answers, but did not; or, if he did, I did not see him.

I understand Parker has begun upon your piece. A long sitting of our Assembly has hitherto hindered me from beginning the Miscellany. I shall write to Dr. Gronovius as you desire.

I wish I had mathematics enough to satisfy myself, whether the much shorter voyages made by ships bound hence to England, than by those from England hither, are not in some degree owing to the diurnal motion. of the earth; and if so, in what degree. It is a notion that has lately entered my mind; I know not if ever any other's. Ships in a calm at the equator move with the sea fifteen miles per minute; at our Cape suppose twelve miles per minute; in the British Channel suppose

will not be quickly forgotten where he was once known; in whom native taste and talent made up so fully for the deficiencies of early education, that he was the intimate friend and favorite companion of the few literary men of his period; and in whose manners and conversation, frankness and urbanity were so happily blended, that, wherever he went, he softened hostility, conciliated good-will, and turned accidental acquaintance into personal and warm friendship" Several admirable letters from him to his son are printed in Professor Mc Vickar's Memoir; in which are also contained many particulars respecting his intercourse with Franklin. EDITOR.

* A printer in New York. - EDITOR.

ten miles per minute. Here is a difference of two miles' velocity per minute between Cape Henlopen and the Lizard. No small matter in so weighty a body as a laden ship, swimming in a fluid. How is this velocity lost in the voyage thither, if not by the resistance of the water? And if so, then the water, which resisted in part, must have given way in part to the ship, from time to time, as she proceeded continually out of parallels of latitude where the earth's motion or rotation was quicker, into others where it was slower. And thus, as her velocity tends eastward with the earth's motion, she perhaps makes her easting sooner. Suppose a vessel lying still in a calm at our Cape could be taken up, and the same instant set down in an equal calm in the English Channel; would not the difference of velocity between her and the sea she was placed in appear plainly by a violent motion of the ship through the water eastward?

I have not time to explain myself farther, the post waiting; but I believe I have said enough for you to comprehend my meaning. If the reasons hinted at should incline you to think there is any thing in this notion, I should be glad of an answer to this question, if it be capable of a precise answer, viz.

Suppose a ship sails in a northeast line from latitude 39 to latitude 52, in thirty days, how long will she be returning on the same line, winds, currents, &c. being equal? Just so much as the eastern motion of the earth helps her easting, I suppose it will hinder her westing. Perhaps the weight and dimensions or shape of the vessel should be taken into consideration, as the water resists bodies of different shapes differently.

I must beg you to excuse the incorrectness of this scrawl, as I have not time to transcribe. I am, Sir, Your most humble servant, B. FRANKLIN.

FROM CADWALLADER COLDEN TO B. FRANKLIN.

Answer to the foregoing Letter respecting the Sailing of Ships across the Atlantic.

SIR,

[Date uncertair.]

There is no question but in the case you mention of a ship's being taken up in a southern latitude, and set down in one some degrees more northerly, at the same moment, she would have a degree of motion eastward; but, that it would shorten a voyage from America to Europe, I cannot think; because, as the alteration is made by insensibly small steps, it can only be so much as an alteration of the velocity in the least conceivable part of a degree of latitude is greater than the resistance of the water, which in all cases remains the same, and equally resists the smallest alteration of the velocity, as the greatest.

Suppose, for example, in the alteration of one second of latitude, how much greater will the velocity be in the southward than northward? If it be sixty miles at the equator, what will it be at one second on either side of the equator? The difference is the force which the ship can acquire from the diurnal rotation of the earth in this second. Now it may be asked, whether this difference will be sufficient to overcome the resistance of the water in any degree whatsoever; that is, whether it be not infinitely small in respect to the resistance of the body of water, which resists the motion of a ship; and if so, it can neither add to, nor diminish, the ship's way in the time she alters her latitude one second; and, if this be the case, it cannot either forward or stop her way in a greater change of latitude, because it is done by a continual addition of seconds,