Benjamin Franklin Papers
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From Benjamin Franklin to [Mary Stevenson], 21 June 1762

To [Mary Stevenson]1

Draft: Library of Congress; copy: American Philosophical Society

Cravenstreet, June 21. 1762

Did you ever see People at work with Spades and Pickaxes, digging a Cellar?

When they have loosen’d the Earth perhaps a foot deep, that loose Earth must be carried off, or they can go no deeper; it is in their way, and hinders the Operation of the Instruments.

When the first foot of loose Earth is removed, they can dig and loosen the Earth a foot deeper.

But if those who remove the Earth, should with it take away the Spades and Pickaxes; the Work will be equally obstructed as if they had left the loose Earth unremoved.

I imagine the Operation of Fire upon Fewel with the Assistance of Air may be in some degree similar to this. Fire penetrates Bodies, and separates their Parts. The Air receives and carries off the Parts separated, which if not carried off would impede the Action of the Fire. With this Assistance therefore of a moderate Current of Air, the Separation encreases; but too violent a Blast carries off the Fire itself; and thus any Fire may be blown out as a Candle by the Breath if the Blast be proportionable.

But if Air contributes inflammatory Matter as some have thought, then it should seem, that the more Air, the more the Flame would be augmented, which beyond certain Bounds does not agree with the Fact.

Some Substances take Fire, i.e. are kindled by the Application of Fire much sooner than others. This is in proportion as they are bad or good Conductors of Fire, and as their Parts cohere with less or more Strength. A bad Conductor of Fire not easily permitting it to penetrate and be absorb’d and its force divided among the whole Substance, its Operation is so much the Stronger on the Surface to which it is apply’d, and is in a small Depth of Surface strong enough to produce the Separation of Parts which we call Burning. Wax, Sulphur, all Oils and Fats and most vegetable Substances are bad Conductors of Fire. The Oil of a Lamp, burning at the Top may be scarce warm at the Bottom; a Candle or a Stick of Wood inflam’d at one End is cool at the other. Metals which are better Conductors are not so easily kindled, tho’ when sufficient Fire is apply’d to them to separate their Parts they will all burn. But the Fire apply’d to their Surfaces enters more easily is absorb’d and divided; and not enough left on the Surface to overcome the Stronger Cohesion of their Parts. A close Contact with Metals will for the same Reason prevent the burning of more inflammable Substances: A flaxen Thread bound close round an Iron Poker, will not burn in the Flame of a Candle; for it must imbibe a certain Quantity of Fire before it can burn, i.e. before its Parts can separate; But the Poker as fast as the Fire arrives, takes it from the Thread, conducts it away and divides it in its own Substance.

Common Fire I conceive to be collected by Friction from the common Mass of that Fluid, in the same manner as the electrical Fluid is collected by Friction, which I have endeavoured to explain in some of my electrical Papers, and to avoid Length in this Letter refer you to them. In Wheels the Particles of Grease and Oil acting as so many little Rollers and Preventing Friction between the Wood and Wood, do thereby prevent the Collection of Fire.

[Elsewhere on this page arranged in a column:2] Col Ludwell / Call at John Hunts / Mrs French / Dr Russell / Wm Do [ditto] / Elias Bland / Brown Charter house / Mr Colepeper / Henry & Cave / Dr Bevis / Mr Wilson Canon street / Newbery / Crosson / Mildred / Aufrere / Sargent / Neat & Neave / Collinson / Post Office / Baker Cards Exp[enses?] / Willock / Dr Reeves / Dr Hadley / Mr Edwards / Memo. Becket Tully Old Age / Ephemerides Motuum / Mr Allen and Miss Downes

[In another column:3] Bellows. / Toys for Children / New Things at Turners. / Tin men Pewterers Brasiers.

Skaining of Worsted into hard twisted Rolls4

1So identified because the letter is clearly a response to hers of June 11 (above, pp. 103–4) and because of a note she added at the bottom of the copy made by her eleven-year-old son, Thomas Tickell Hewson, many years later: “Transcribed by T. T. Hewson from a rough copy of a letter written by Dr. Franklin, intended for me, but never finished, nor shewn to me till at Passy Dec. 1784. M.H.”

2BF probably compiled this list, through parts of which lines are drawn, to remind himself of people he wanted to see before he left London. Col. Philip Ludwell (above, VI, 532 n) was a Va. planter and official who moved to London in 1760 and who commissioned the Mason Chamberlain portrait of BF in July or August 1762. John Hunt (above, VII, 373 n) was a London Quaker merchant who had been sent by the English Friends as an adviser to the Pa. Quakers in 1756. Mrs. French was possibly the Katherine French whose inadequately dated notes inviting BF for music, chess, and literary discussions seem to belong to the period of 1765–71. Alexander Russell (1715?–1768), M.D., F.R.S., was a distinguished physician and naturalist, a friend of Fothergill and Collinson; DNB. His brother William, also F.R.S., was secretary to the Levant Co. Elias Bland (above, III, 141 n) was another London Quaker merchant; BF had lent him £300, July 12, 1759, which Bland repaid about four weeks later; “Account of Expences,” pp. 42, 45; PMHB, LV (1931), 121; see also below, p. 139 n. There were two Browns living at the Charterhouse as pensioners at this time: Thomas, admitted 1755, died Nov. 12, 1762; and John Walker, admitted 1748, died Feb. 7, 1769; “The Registers and Monumental Inscriptions of Charterhouse Chapel,” Registers, XVIII, Publications, Harleian Soc. Which was BF’s friend is not known. Mr. Colepeper has not been identified. Henry & Cave, the firm which published Gent. Mag., consisted at this time of David Henry (1725?–1792) and Richard Cave, a nephew of Edward Cave, the founder. John Bevis (above, IV, 392 n) was an astronomer who also participated in electrical experiments. “Mr. Wilson Canon Street” was apparently not Benjamin Wilson (above, IV, 391 n), the painter and electrician, who lived at this time in Great Queen Street. Newbery was probably John Newbery, publisher of Johnson, Goldsmith, and other writers (above, VI, 279 n). Crosson was probably the tradesman from whom BF and WF had bought stockings and other clothing; “Account of Expences,” p. 39; PMHB, LV (1931), 118. Daniel Mildred was a member of the mercantile firm of Mildred & Roberts. George Aufrere and John Sargent composed the firm of Sargent Aufrere & Co., merchants, who handled payment of the bills drawn on BF by the trustees of the Pa. Loan Office. William Neate and Richard Neave comprised another London mercantile firm with which BF had occasional business relations for many years (above, IV, 115). Peter Collinson (above, III, 115–16 n), one of BF’s oldest and closest friends, needs no further identification. A visit to the General Post Office before departure would be an obvious duty for the deputy joint postmaster general of America. Baker is unidentified. Robert Willock was a bookseller at Sir Isaac Newton’s Head from 1735 or earlier to 1767. Dr. Thomas Reeves was a London physician who attended Peter Collinson in his last illness six years later. John Hadley (above, VIII, 108), was the professor of chemistry at Cambridge with whom BF had performed experiments on evaporation in June 1758. Mr. Edwards may have been George Edwards (1694–1773), F.R.S., a distinguished ornithologist. Thomas Becket was the publisher of BF’s Canada Pamphlet; BF left orders with him for pamphlets to be sent to America (below, p. 393) and gave Strahan some copies of his own printing of Cicero’s Cato Major (“Tully Old Age”) to deliver to Becket for sale (below, p. 108). Ephemerides motuum coelestium was a common title for almanacs. Mr. T. Allen was the brother-in-law of Elizabeth Downes, the girl WF married September 4, 1762.

3Like every good family man returning home after a long absence, BF was obviously planning to bring presents for relatives, close friends, and those friends’ children.

4On another part of the same page with the memoranda printed above BF wrote this caption and drew the sketch reproduced opposite. Whether he did this at about the same time that he drafted the letter or much later is not known.

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