Benjamin Franklin Papers

Guillaume Mazéas to Stephen Hales, 20 May 1752

Guillaume Mazéas to Stephen Hales7

Printed in The Royal Society, Philosophical Transactions, XLVII (1751–52), 534–6.8

St. Germain, May 20, 1752, n.s.


The favour done me by the Royal Society obliging me to interest myself in whatsoever concerns their honour, I beg you will communicate the following account.

The Philadelphian experiments, that Mr. Collinson, a member of the Royal Society, was so kind as to communicate to the public, having been universally admired in France, the King desired to see them performed. Wherefore the Duke D’Ayen9 offer’d his Majesty his country-house at St. Germain, where M. de Lor, master of experimental philosophy,1 should put those of Philadelphia in execution. His Majesty saw them with great satisfaction, and greatly applauded Messieurs Franklin and Collinson. These applauses of his Majesty having excited in Messieurs de Buffon,2 D’Alibard, and De Lor, a desire of verifying the conjectures of Mr. Franklin, upon the analogy of thunder and electricity, they prepar’d themselves for making the experiments.

M. D’Alibard chose, for this purpose, a garden situated at Marly, where he placed upon an electrical body a pointed bar of iron, of 40 feet high. On the 10 of May, 20 minutes past 2 afternoon, a stormy cloud having passed over the place where the bar stood, those, that were appointed to observe it, drew near, and attracted from it sparks of fire, perceiving the same kind of commotions as in the common electrical experiments.

M. de Lor, sensible of the good success of this experiment, resolved to repeat it at his house in the Estrapade at Paris. He raised a bar of iron 99 feet high, placed upon a cake of resin, two feet square, and 3 inches thick. On the 18 of May, between 4 and 5 in the afternoon, a stormy cloud having passed over the bar, where it remain’d half an hour, he drew sparks from the bar. These sparks were like those of a gun, when, in the electrical experiments, the globe is only rubb’d by the cushion, and they produced the same noise, the same fire, and the same crackling. They drew the strongest sparks at the distance of 9 lines,3 while the rain, mingled with a little hail, fell from the cloud, without either thunder or lightning; this cloud being, according to all appearance, only the consequence of a storm, which happen’d elsewhere.

From this experiment we conjectur’d, that a bar of iron, placed in a high situation upon an electrical body, might attract the storm, and deprive the cloud of all its thunder. I do not doubt but the Royal Society has directed some of its members to pursue these experiments, and to push this analogy yet further.

I do not know, Sir, whether Mr. Franklin’s letters were before your considerations upon earthquakes:4 if they were, we are oblig’d to Mr. Collinson for his communication of Mr. Franklin’s notions; if they are not, you deserve the honour of the discovery; and whosesoever it be, it is still to the Royal Society we owe the communication of this ingenious thought, which the experiments of M. D’Alibard and M. De Lor have confirm’d. These two learned men deserve that esteem of our nation, which their talents have a long time procured them. I am, with a profound respect, Sir, Your most humble, and obedient servant,

G. Mazeas

[Note numbering follows the Franklin Papers source.]

7Guillaume Mazéas (1720–1775), canon of Vannes, correspondent of the Academy of Sciences, Paris, and F.R.S., London; translator of English scientific works into French. Stephen Hales (1677–1761), D.D., F.R.S., perpetual curate of Teddington; botanical and animal physiologist; inventor of a system of artificial ventilation for prisons, ships, granaries, and other structures.

8The heading in Phil. Trans. adds: “Translated from the French by James Parsons, M.D., F.R.S.” The French original has not been found. With the omission of the first paragraph and the last two, this letter was reprinted in the 1769 and 1774 editions of Exper. and Obser.

9Louis de Noailles (1713–1793), eldest son of Adrien-Maurice, duc de Noailles, whom he succeeded in the title, 1766; himself created duc d’Ayen, 1737; army officer, promoted to lieutenant general, 1748, and maréchal de France, 1775; personal friend of Louis XV.

1Delor has not been fully identified. In a footnote to the preface of his translation of Exper. and Obser., 1752, p. 20, Dalibard states that Delor “démontre toutes ces nouvelles expériences électriques avec les anciennes dans les cours publics de Physique expérimentale qu’il fait avec un applaudissement général dans son magnifique cabinet place de l’Estrapade à Paris.” A reviewer in Memoires pour l’Histoire des Sciences & des beaux Arts (June 1752), p. 1211, speaks warmly of “son Cabinet, ses machines, son addresse et son honnêteté.” He is not listed among the members of the Royal Academy of Sciences.

2On Buffon, see above, III, 111 n.

3A Paris line, one-twelfth of a French inch, is 0.0888 of an English inch. Nine lines, therefore, make a little more than three-fourths of an English inch.

4A series of earthquakes in England and on the Continent in 1750 brought to the Royal Society a large number of papers describing incidents or discussing the causes of the phenomenon. Fifty-seven were printed as an appendix to Phil. Trans., XLVI (1749–50). In one of these (pp. 669–81) Stephen Hales, Mazéas’ correspondent, suggested a causal relationship between earthquakes and electricity, but made no mention of BF. See above, III, 477. In three papers (pp. 641–6, 657–69, 731–50) Rev. William Stukeley (1687–1765), M.D., F.R.S., undertook to show that earthquakes are caused by electricity, citing BF’s “very pretty Discourse … concerning Thundergusts, Lights, and like Meteors” (see above, III, 365–76). Stukeley argued that, if thunder was caused by an electrical discharge between clouds, as he believed BF had proved, then “from the same Principle I infer, that, if a non-electric Cloud discharges its Contents, upon any Part of the Earth, when in a high-electrify’d State, an Earthquake must necessarily ensue.” Several other writers discussed the possible connection between lightning and earthquakes, some agreeing with Stukeley, at least in part, others disagreeing. Stukeley revised and published his papers as a pamphlet, The Philosophy of Earthquakes, Natural and Religious (London, 1750), a copy of the third edition of which (London, 1756) he inscribed and sent “To Benjamin Franklin Esq. Father of Electricity.” Cohen, BF’s Experiments, p. 91. This paragraph in Mazéas’ letter was omitted when it was reprinted in the 1769 and 1774 editions of Exper. and Obser., possibly because BF wished to dissociate himself from the hypothesis that earthquakes are caused by electrical discharges.

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