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’Ayen offer’d his Majesty his country-house at St. Germain, where M. de Lor, master of experimental philosophy, 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, 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, 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: 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,