Benjamin Franklin Papers

From Benjamin Franklin to Cadwallader Colden, 6 December 1753

To Cadwallader Colden

Letter: ALS: New-York Historical Socity; enclosure: draft: American Philosophical Society

Philada. Dec. 6. 1753

Dear Sir

I receiv’d your Favour of the 29th past, with some Remarks on my meteorological Paper,3 for which I thank you, and return some Observations on those Remarks, hoping by this Friendly Intercourse of Sentiments and Objections, some Advantage will arise to the Increase of true Knowledge.

I sent you our Treaty4 some time since; you will find very little in it: But I have hopes it will introduce a Regulation of our Indian Trade, by the Government taking it in hand, and furnishing the Indians with Goods at the cheapest Rate without aiming at Profit, as is done by the Massachusetts; by which Means I think we must vastly undersell the French, and thereby attach the Indians more firmly to the British Interest.5

Mr. Collinson certainly received your Answer to Kastner;6 I think one of his Letters to me mentions it.

I send you herewith a Copy of my Paper on the Increase of Mankind; the only one I have, so must request you to return it. That on the Air, &c. is what you have already seen. The third mention’d to you by Mr. Collinson, concerning the Germans is scarce worth sending, it will contain nothing new to you.7

I congratulate you on L. Halifax’s Approbation of your Conduct in Publick Affairs. From such a Man the Honour is great, and the Satisfaction; But the Approbation of your own Mind is something more valuable in itself, and it is what I doubt not you will always enjoy.

I should like to see Pike’s Book some time or other when you can conveniently send it.1

With great Esteem and Respect, I am, Sir, Your most obedient humble Servant

B Franklin

C. Colden Esqr.


Answer to the foregoing Observations2

I agree with you, that it seems absurd to suppose that a Body can act where it is not. I have no Idea of Bodies at a Distance attracting or repelling one another without the Assistance of some Medium, tho’ I know not what that Medium is, or how it operates. When I speak of Attraction or Repulsion I make use of those Words for want of others more proper, and intend only to express Effects, which I see, and not Causes, of which I am ignorant. When I press a blown Bladder between my Knees, I find I cannot bring its Sides together, but my Knees feel a Springy Matter pushing them back to a greater Distance, or repelling them. I conclude that the Air it contains is the Cause. And when I operate on the Air, and find I cannot by Pressure force its Particles into Contact, but they still spring back against the Pressure, I conceive there must be some Medium between its Particles that prevents their Closing, tho’ I cannot tell what it is. And if I were acquainted with that Medium, and found its Particles to approach and recede from each other according to the Pressure they suffer’d, I should imagine there must be some finer Medium between them by which these Operations were performed.

I allow that increase of the Surface of a Body may occasion it to descend slower in Air, Water, or any other Fluid; but do not conceive therefore that it lessens its Weight. Where the increas’d Surface is so dispos’d as that in its falling a greater Quantity of the Fluid it sinks in must be moved out of its Way, a greater Time is required for such Removal. Four square Feet of sheet Lead sinking in Water broadways, cannot descend near so fast as it would edgeways, yet its Weight on the Hydrostatic Ballance would I imagine be the same, whether suspended by the Middle or by a Corner.

I make no doubt but that Ridges of high Mountains do often interrupt, stop, reverberate or turn the Winds that blow against them, according to the different degrees of Strength of the Winds, and the Angles of Incidence. I suppose too, that the cold upper Parts of Mountains may condense the warmer Air that comes near them, and so by making it specifically heavier, cause it to descend on one or both sides of the Ridge into the warmer Valleys, which will seem a Wind blowing from the Mountain.

Damp Winds tho’ not colder by the Thermometer, give a more uneasy sensation of Cold than dry ones. Because (to speak like an Electrician), they conduct better, that is, are better fitted to convey away the Heat from our Bodies; The Body cannot feel without itself; Our Sensation of Cold is not in the Air without the Body, but in those Parts of the Body which have been depriv’d of their Heat by the Air. My Desk and its Lock are, I suppose of the same temperament when they have long been expos’d to the same Air; but now, if I lay my Hand on the Wood, it does not seem so cold to me as the Lock; because (as I imagine) Wood is not so good a Conductor to receive and convey away the Heat from my Skin and the adjacent Flesh, as Metal is. Take a Piece of Wood of the Size and Shape of a Dollar between the Thumb and Fingers of one Hand, and a Dollar in like manner with the other Hand; place the Edges of both at the same time in the Flame of a Candle; and tho’ the Edge of the wooden Piece takes Flame and the metal Piece does not, yet you will be oblig’d to drop the latter before the former, it conducting the Heat more suddenly to your Fingers. Thus we can without Pain handle Glass and China Cups fill’d with hot Liquors, as Tea, &c. but not silver ones. A Silver Teapot must have a Wooden Handle. Perhaps it is for the same Reason that woolen Garments keep the Body warmer than Linen ones equally thick. Woolen keeping the Natural Heat in, or, in other Words, not conducting it out to Air.

In Regard to Waterspouts, having in a long Letter to [a] Gentleman of the same Sentiment with you as to their Direction3 said all that I have to say in support of my Opinion, I need not repeat the Arguments therein contain’d, as I intend to send you a Copy of it,4 by some other Opportunity for your Perusal. I imagine you will find all the Appearances you saw, accounted for by my Hypothesis. I thank you for communicating this Account of them. At present I would only say, that the Opinion of Winds being generated in Clouds by Fermentation, is new to me, and I am unacquainted with the Facts on which it is founded: I likewise find it difficult to conceive of Winds confin’d in the Bodys of Clouds, which I imagine have little more solidity than the Fogs on the Earth’s Surface. The Objection from the Freshness of Rain Water is a strong one, but I think I have answered it in the Letter above mentioned, to which I must beg Leave at present to refer you.

[Note numbering follows the Franklin Papers source.]

3See above, pp. 121–6.

4A Treaty held with the Ohio Indians, at Carlisle, In October, 1753 (Phila., 1753), reprinted above, pp. 84–107.

5On BF’s interest in regulating the Indian trade, see above, pp. 79–80, 111, 121.

6Writing Colden, Oct. 18, 1753, Collinson said he had received “Kastner’s” (Colden Paps., IV, 408), possibly the reply to Kästner. BF told Colden, April 12, 1753 (above, IV, 463), that he was sending the reply to the German professor, “corrected as you direct,” the next week; and Collinson mentions to BF, July 20, a letter from BF of April 17, which has not been found, which may have contained the reply to Kästner.

7See Collinson to Colden, Sept. 1, 1753, in Colden Paps., IV, 406; and above, IV, 477–86.

1See above, p. 123. Colden sent the book, which BF returned Aug. 30, 1754.

2See above, p. 124. Read in the Royal Society, Nov. 4, 1756, and printed in the 1769 edition of Exper. and Obser., pp. 258–61. The title was probably added when the piece was printed.

3See above, pp. 125–6.

4See above, IV, 429.

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