Benjamin Franklin Papers

Franklin’s Responses to the Maréchale de Beauvau’s Questions on Lightning Rods, [after 21 July 1783]

Franklin’s Responses to the Maréchale de Beauvau’s Questions on Lightning Rods

D:4 American Philosophical Society

On July 21, 1783, Bethia Alexander wrote to William Temple Franklin with a request from the maréchale de Beauvau, who was desperate for Franklin’s advice on installing a lightning rod at her residence, the château du Val.5 Temple was to place before his grandfather the paper she enclosed. “Une reponse tres exacte” was to be written in the margin beside each question, and the paper returned to Alexander “bien vite.” Do hurry, she repeated, because if you delay, and if a lightning bolt should lack the decency to wait until the answers arrive, you will be filled with remorse.

Lightning rods were still relatively new to Paris. When the first two were installed in December, 1782, under the supervision of the abbé Bertholon (who had installed several in his native Lyon and elsewhere), the Mercure de France published their locations and dimensions, praised the abbé, and announced, with obvious relief, that Paris no longer lagged behind the countryside in this important development.6 Any lingering doubts about the safety of these devices must have been allayed when, in a highly anticipated ruling of May 31, the appeals court at Artois ordered Vyssery de Bois-Valée’s lightning rod reinstated in Saint-Omer.7

The urgency in this request from the maréchale de Beauvau, however, was surely due to the terrifying storms that had been sweeping across France, causing widespread destruction and loss of life. “Extraordinary lightning” was reported in the Paris region on July 2 and 3—14 strikes in one area, with four people killed—and again on July 15. Reports were also published of lightning strikes, ground tremors (were they subterranean thunder?), high winds, and torrential rains in the provinces. Adding to the general disquietude was the fact that since June the temperature had been unusually hot and the atmosphere clouded by a mysterious, smoke-like “dry fog” that obscured the sun’s rays. La Lande and others wrote articles for the Journal de Paris attempting to reassure the frightened population that these conditions did not presage a major earthquake, like the recent one in Calabria. In the months and years to come, scientists throughout Europe would publish theories on the cause of this dry fog. Franklin himself speculated on possible causes in May, 1784.8

At the château du Val, it was the maréchale’s husband who made the first inquiries about lightning rods, seeking advice from St. John de Crèvecœur, who was a regular guest at the family’s Sunday dinners during the spring and early summer of 1783. Crèvecœur, according to his later account, recommended that a lightning rod be mounted atop a very tall mast in the middle of the courtyard—a plan, he claimed, that Franklin approved. In spite of the answers printed here that Franklin evidently returned to the maréchale, which hardly recommended it as a first choice, a mast was indeed constructed. Made from two poplar trunks grafted together, the pole, raised before a large crowd of friends, elevated the tip of a 12-foot lightning rod 89 feet into the sky. According to Crèvecœur, the structure created a sensation and caused many other “grands seigneurs” to protect their properties.9

[after July 21, 1783]


Avant de placer un Conducteur ou Paratonnere il est nécessaire que quelqu’un qui s’y entend bien, voye le Batiment qui est destiné a etre garanti de la foudre.

Dans un étendu aussi considerable que celle de 45 Toises, on croit qu’il sera bien d’eriger 4 Conducteurs à égale distance les uns des Autres, & communiquants ensemble par un barre de Fer sur le Toit du Batiment.


Il doit etre environ dix a douze Pieds plus haut que la partie la plus elevée du Batiment. 3. Il doit etre appliqué immediatement à la muraille.

4 Un Mât n’est pas necessaire pour le Soutient du Conducteur.

On trouvera cette Matiere très detaillé dans l’Ouvrage de M. Franklin sur l’Electricité.— Et on fera bien d’employer un des Ouvriers de Versailles ou de Paris, qui ont deja construit des Conducteurs.

[Note numbering follows the Franklin Papers source.]

4We surmise that this text, written in labored French by WTF on a torn sheet of paper, is his translation of responses that BF drafted in English. The French answers were doubtless copied onto Mme de Beauvau’s sheet of questions and returned in accordance with Bethia Alexander’s letter to WTF described in the headnote. This sheet is filed with Alexander’s letter.

5The château was in the forest of Saint-Germain, not far from the Alexanders’ estate. Marie-Charlotte-Sylvie (Elisabeth-Charlotte) de Rohan-Chabot, princesse de Beauvau-Craon (1729–1807), was the wife of Charles-Just, maréchal prince de Beauvau-Craon, a distinguished military man and member of the Académie française and the Accademia della Crusca: DBF, under Beauvau; Dictionnaire de la noblesse, II, 740, 742; Georges Poull, Fléville: son histoire et ses seigneurs, XIIIe s.–XIXe s. (Rupt sur Moselle, 1988), pp. 122–6; Julia P. Mitchell, St. Jean de Crèvecoeur (New York, 1916), p. 81.

6Mercure de France (Jour. politique de Bruxelles), Dec. 28, 1782, pp. 188–9. In vol. 38 we stated that the first lightning rods in Paris were installed in December, 1783, citing an otherwise scrupulous work that misreported the year of this article in the Mercure and a personal letter written the same month by Bertholon: XXXVIII, 436n.

7For the case see XXXVIII, 435–8; XXXIX, 237–8. The extensive brief published in November, 1782, by Buissart, the chief lawyer, was much discussed in Paris throughout the following spring: Jessica Riskin, Science in the Age of Sensibility: the Sentimental Empiricists of the French Enlightenment (Chicago and London, 2002), p. 175. Buissart left the oral arguments in May, 1783, to his junior colleague, Maximilien Robespierre; they are discussed in ibid., pp. 176–84. The court’s decision was announced in the Mercure de France (Jour. politique de Bruxelles), June 21, 1783, pp. 135–7, where Robespierre was described as a young lawyer “d’un mérite rare” who had displayed “une éloquence & une sagacité qui donne la plus haute idée de ses connoissances.”

8For reports on the extreme weather conditions see the Jour. de Paris of July 1, 2, 9, 16, 21 (supp.), and 22, 1783; Mercure de France (Jour. politique de Bruxelles), July 12 and 26, 1783, pp. 77–8, 175–6. In “Meteorological Imaginations and Conjectures,” BF speculated that the fog of the previous summer might have been caused by burning celestial bodies whose smoke was trapped in the atmosphere or by volcanic dust from the recent eruptions in Iceland: Smyth, Writings, IX, 215–18.

9Robert de Crèvecœur, Saint John de Crèvecoeur, sa vie et ses ouvrages (1735–1813) (Paris, 1883), pp. 72–3. After a July 10 electrical storm in Normandy, where he then was staying, Crèvecœur also convinced more than 20 people to install lightning rods on their homes, and insisted that a lightning rod be installed on the ship that carried him back to New York, the Courrier de l’Europe; see Mitchell, St. Jean de Crèvecoeur, pp. 81–4.

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