Benjamin Franklin Papers

From Benjamin Franklin to Ebenezer Kinnersley, 28 July 1759

To Ebenezer Kinnersley

MS not found; reprinted from The Pennsylvania Magazine of History and Biography, XIII (1889), 247–8.

London, July 28, 1759.

Dear Sir,

I received your favour of Sept. 96 and should have answer’d it sooner, but delay’d in Expectation of procuring for you some Book that describes and explains the Uses of the Instruments you are at a loss about. I have not yet got such a Book but shall make further Enquiry. Does not Desaguliers in his Course explain them?7 You do not mention the Reasons of your being tired of your Situation in the Academy.8 And if you had, it would perhaps be out of my Power at this Distance to remedy any Inconveniences you suffer or even if I was present. For before I left Philadelphia, everything to be done in the Academy was privately preconcerted in a Cabal without my Knowledge or Participation and accordingly carried into Execution. The Schemes of Public Parties made it seem requisite to lessen my Influence whereever it could be lessened. The Trustees had reap’d the full Advantage of my Head, Hands, Heart and Purse, in getting through the first Difficulties of the Design, and when they thought they could do without me, they laid me aside.9 I wish Success to the Schools nevertheless and am sorry to hear that the whole Number of Scholars does not at present exceed an hundred and forty.

I once thought of advising you to make Trial of Your Lectures here, and perhaps in the more early Times of Electricity it might have answer’d;1 but now I much doubt it, so great is the general Negligence of every thing in the Way of Science that has not Novelty to recommend it. Courses of Experimental Philosophy, formerly so much in Vogue, are now disregarded; so that Mr. Demainbray,2 who is reputed an excellent Lecturer, and has an Apparatus that cost nearly £2000, the finest perhaps in the World, can hardly make up an audience in this great City to attend one Course in a Winter.

I wonder your roughening the Glass Globe3 did not succeed. I have seen Mr. Canton4 frequently perform his Experiments with the smooth and rough Tubes, and they answered perfectly as he describes them in the Transactions.5 Perhaps you did not use the same Rubbers.

There are some few new Experiments here in Electricity which at present I can only just hint to you. Mr. Symmer6 has found that a new black Silk Stocking worn 8 or 10 Minutes on a new white one, then both drawn off together, they have, while together, no great Signs of Electricity; i.e. they do not much attract the small Cork Balls of Mr. Canton’s Box; but being drawn one out of the other, they puff out to the full Shape of the Leg, affect the Cork Balls at the Distance of 6 Feet and attract one another at the Distance of 18 inches and will cling together; and either of them against a smooth Wall or a Looking Glass, will stick to it some time. Upon Trial, the black Stocking appears to be electris’d negatively, the white one positively. He charges Vials with them as we us’d to do with a Tube. Mr. Delavall has found that several Bodies which conduct when cold, or hot to a certain Degree, will not conduct when in a middle State.7 Portland Freestone, for Instance, when cold, conducts; heated to a certain degree will not conduct; heated more it conducts again; and as it cools, passes thro’ that Degree in which it will not conduct till it becomes cooler.

This with what you mention of your Cedar Cylinder, makes me think, that possibly a thin Cedar Board, or Board of other Wood, thoroughly dried and heated, might if coated and electrified, yield a Shock as glass Planes do. As yet I have not try’d it.8

But the greatest Discovery in this Way is the Virtue of the Tourmalin Stone, brought from Ceylon in the Indies which being heated in boiling Water, becomes strongly electrical, one side positive, the other negative, without the least Rubbing.9 They are very rare but I have two of them and long to show you the Experiments.

Billy joins with me in Compliments to you and to good Mrs. Kinnersley and your promising Children. I am with much Esteem and Affection Dear Sir, Your most obedient Servant.

B. Franklin.

Mr. Kinnersley.

[Note numbering follows the Franklin Papers source.]

6Not found.

7John Theophilus Desaguliers, A Course of Experimental Philosophy (2 vols., London, 1734–44). Collinson had suggested this book as a possible guide for the selection of instruments for the Academy; see above, IV, 3–4.

8Kinnersley was at this time master of the English School and professor of English and oratory in the College of Philadelphia. Personal illness; the Trustees’ neglect of the English School, the enrollment of which had dropped more than half; and perhaps a realization that he was not as gifted a teacher as his predecessor David James Dove had been, were probable factors in Kinnersley’s disenchantment. He held his position, however, until 1772. Montgomery, Hist. Univ. Pa., pp. 244–51, 342.

9Richard Peters was elected president of the trustees, in BF’s place, May 11, 1756; see above, VII, 12 n.

1For Kinnersley’s lectures in electricity, see above, IV, 192 n.

2After lecturing on electricity in the British Isles and then in France in the 1740s and 1750s, Stephen Charles Triboudet Demainbray (1710–1782) returned to England and in 1754 became the tutor of the Prince of Wales in mathematics, experimental philosophy, and natural history. In 1768, his former pupil, now George III, appointed him astronomer at the royal observatory at Kew. DNB.

3On Dec. 5, 1757, BF recorded the purchase of a globe for Kinnersley. “Account of Expences,” p. 9; PMHB, LV (1931), 106.

4For John Canton, F.R.S., English electrical experimenter, and twice winner of the Copley Medal, see above, IV, 390 n.

5See Phil. Trans., XLVIII (1754), 780–5. There Canton sought to demonstrate that “the positive and negative powers of electricity” could be “produced at pleasure” by altering the surface of a glass tube and by rubbing it with different substances. See also I. Bernard Cohen, Franklin and Newton (Phila., 1956), pp. 534–7.

6Robert Symmer (above, IV, 276–7 n) published four papers on the electrical properties of silk in Phil. Trans., LI (1759), 340–89. In one of these (pp. 374–7) he mentioned that he had used BF’s electrical apparatus and had conducted some experiments in his presence.

7For these experiments by Edward Hussey Delaval, the first man BF helped to nominate for membership in the Royal Society (above, pp. 359–60), see Phil. Trans., LI (1759), 83–8.

8Kinnersley reported another experiment with cedar in his letter to BF of March 12, 1761.

9See above, pp. 393–6.

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