Benjamin Franklin Papers

Jonathan Todd to Jared Eliot, 6 March 1753

Jonathan Todd9 to Jared Eliot

ALS: American Philosophical Society10

East Guilford, March. 6. Anno Domi 1753

Revd and Dear Sir,

I number it among the fortunate Occurrences of my Life that I have been indulged an Interest in your Friendship. I wish I could better deserve it. Amongst many other agreable Pleasures this Way deriv’d, I esteem it a considerable One, to enjoy the Benefit of Seeing now and then Some entertaining Pieces communicated to your Self by Some of your ingenious Correspondents. Amongst all of which I have not been better pleased with any, than those ingenious Pieces of Mr. Franklin you have favour’d me with the Reading of.

I have Sometimes almost come to a Determination to endeavour by your Assistance to get into an Acquaintance with that Gentleman, a chief one in the Republick of Letters, whose Parts, Industry and Learning are known in both Englands; and devoted to the Welfare of Mankind.

But considering the Barreness of my Genius, cramp’d by my low Circumstances and many other Disadvantages, I have been discourag’d from pursuing the Same. It is doubtless fit that I be contented with the Privilege of enjoying in Some Measure the Benefit of the Correspondence between Him and yourself. I remember the Satyrical Lines of Persius:

Respue quod non es, tollat sua munera cerdo:

Tecum habita, et noris quam sit tibi curta Supellex.1

However, Dear Sir, I venture to trouble you with two or three Thoughts that came into my Mind, in reading that curious Manuscript, which you last favour’d me with the Sight of, intitl’d, Physical and Meteorological Conjectures &c.2 which, if you please you may communicate to that learned Gentleman, not so much as real Objections to his Conjectures and Suppositions, but, as imaginary Ones to be entirely removed by Him, when he revises the Same.

“Air and Water mutually attract each other,” saith that Gentleman: “Hence Water will dissolve in Air, as Salt in Water.” I think, that he hath demonstrated, that the Supporting of Salt in Water, is not owing to its Superficies being increas’d, because the Specifick Gravity of Salt is not alter’d by dividing of it, any more than that of Lead; Sixteen Bullets of which, of an ounce each, weigh as much in Water as One, of a Pound. But yet, when this came to be applied to the Supporting of Water in Air, I found an Objection rising in my Mind.

In the first Place, I have always been loth to Seek for any new Hypothesis, or particular Law of Nature to account for any Thing that may be accounted for, from the known general and universal Laws of Nature: It being an Argument of the infinite Wisdom of the Author of the World to effect so many Things by one general Law. Now I had thought that the rising and Support of Water in Air might be accounted for from the general Law of Gravitation, by only Supposing the Spaces occupied by the Same Quantity of Water increas’d.

And with Respect to the Lead, I queried thus in my own Mind, whether if the Superficies of a Bullet of Lead should be increas’d four or five fold by an internal Vacuity, it would weigh the Same in Water as before. I mean if a Pound of Lead Should be formed into a hollow Globe empty within, whose Superficies Should be four or five Times as big as that of the Same Lead, when a Solid Lump, it would weigh as much in Water as before. I suppos’d it would not. If this Concavity was filled with Water, perhaps it might: If with Air, it would weigh, at lest, as much less as the Difference between the Weight of the included Air and that of Water.

Now altho’ this would do nothing to account for the Dissolution of Salt in Water, the Smallest Lumps of Salt being no more hollow Spheres, or anything of the like Nature than the greatest, yet perhaps it may account for Water’s rising and being Supported in Air. For we know that Such hollow Globles or Bubbles abound upon the Surface of the Waters; which even by the Breath of our Mouths we can cause to quit the Water, and rise in the Air.

These Bubbles, I us’d to suppose to be Coats of Water containing within them Air rarified and expanded with Fire; and that therefore the more Friction and Dashing there is upon the Surface of the Waters, and the more Heat and Fire, the more they abound.

And I us’d to think that altho’ Water be specifically heavier than Air, yet such a Bubble filled only with Fire and very rarify’d Air may be lighter than a Quantity of common Air of the Same cubical Dimensions; and therefore ascend. For the rarifi’d Air inclosd may more fall short of the Same Bulk of common Air in Weight, than the watery Coat exceeds a like Bulk of common Air in Gravity.

This was the Objection in my Mind, tho’, I must confess I know not how to account for the watry Coat’s encompassing the Air as above mention’d; without allowing the Attraction between Air and Water, which the Gentleman Supposes. So that I don’t know but that this Objection examin’d by that Sagacious Genius will be an additional Confirmation of the Hypothesis.

The Gentleman observes, that “A certain Quantity of Moisture should be every Moment discharg’d and taken away from the Lungs,” and hence accounts for the Suffocating Nature of Snuffs of Candles, as impregnating the Air with Grease, between which and Water there is a natural Repellency, and of Air that hath been frequently breathed in, which is overloaded with Water; and for that Reason can take no more Air. Perhaps the same Observation will account for the Suffocating Nature of Damps in Wells.

But then, if the Air can Support and take off but Such a Proportion of Water, and it is necessary that Water be so taken off from the Lungs, I queried with myself, how it is we can breath in an Air full of Vapours, so full as that they continually precipitate. Dont we see the Air overloaded, and casting forth Water plentifully, when there is no Suffocation?

The Gentleman again observes, that “The Air under the Equator and between the Tropicks being constantly heated and rarified by the Sun, rises; it’s Place is Supplied by Air from Northern and Southern Latitudes, which coming from Parts where the Air and Earth had less Motion, and not Suddenly acquiring the quicker Motion of the Equatorial Earth, appears an East Wind blowing westward. The Earth moving from West to East and Slipping under the Air.”

In reading this two Objections occur’d to my mind.

First, that it is Said the Trade Wind doth not blow in the Forenoon but only in the Afternoon.

Secondly, that either the Motion of the Northern and Southern Air towards the Equator is so Slow as to acquire almost the same Motion as the Equatorial Air, when it arrives there, So that there will be no Sensible Difference, or else the Motion of the Northern and Southern Air towards the Equator is quicker and must be Sensible, and then the Trade Wind must appear either as a South East or Northeast Wind: South of the Equator a South East Wind; North of the Equator, a Northeast. For the apparent Wind must be compounded of the Motion from North to South or Vice versa, and of the Difference between it’s Motion from West to East, and that of the Equatorial Air.

Sir. Notwithstanding these Objections I am greatly pleas’d with that Manuscript: It is the most Satisfying Solution of many Pheenomena of Nature I have seen. And ’tis not because I am not charmed with the Piece, that I desire you to present these Objections to that ingenious Gentleman; tis only to give him an Opportunity to remove them. If you think it will be too much Trouble to the Gentleman, to be so lengthy in them as I have been, you may represent them as Short as you please. I am &c.

Jonathan Todd

[Note numbering follows the Franklin Papers source.]

9Jonathan Todd (1713–1791), B.A., Yale, 1732; minister at East Guilford (now Madison), Conn., from 1733 until his death. Though over-humble and unimpressive in appearance and manner, he had a vigorous mind and was well read in the classics, history, and natural philosophy; and several of his sermons were printed. Dexter, Biog. Sketches, I, 465–8. For an interesting and characteristic letter, written in “the old age of a lover of knowledge,” see Todd to Ezra Stiles, Feb. 26, 1783, in Isabel M. Calder, ed., Letters and Papers of Ezra Stiles (New Haven, 1933), pp. 54–7.

10With the omission of the three first paragraphs and the last, BF submitted this letter to the Royal Society (where it was read Nov. 4, 1756), and printed it in Exper. and Obser., 1769 edit., pp. 247–50. He answered Todd’s objections in a letter to Jared Eliot, May 3 (see below, p. 472x), which he printed directly after Todd’s letter in Exper. and Obser.

1Persius, Satires, IV: 51–2.

2See above, p. 235.

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