From David Rittenhouse
ALS: American Philosophical Society
Philadelphia April 29th. 1780
Amidst the many important objects of your attention I doubt not but you sometimes unbend your mind by an Excursion thro’ the fields of Philosophy, I shall therefore make no apology for communicating to you a freak of Nature which seems to be new, at least it is so to us. On the 19th. of August last during a heavy Shower of Rain, not attended by any Thunder lightning or wind, a prodigious Torrent fell on the North or Blue Mountain 10 Miles from Carlisle, and Carried away every Rock and Tree however large that stood in its Course, it likewise tore up the Earth & Stones from 4 to 10 feet deep, and from two to 6 perchers wide, for upwards of 100 rod, that is from very near the top of the Mountain down to the foot of the first Steep Ascent.2 I had heard such wonderful accounts of the effects of this Cataract that I was induced to take a ride of 130 miles to view the Spot, and spent a whole Day there with satisfaction and astonishment. The facts I am perfectly convinced of by my own observation, and which appear to me most worthy of your notice are these. It was certainly a stream of water falling from the Clouds in a Spot not above 10 yards diameter, and not any Collection of waters falling in rain, on the surface of the Earth. The face of the mountain will not admit a possibility of suppoing it to have been a collection of water already fallen in rain the common way, it being a very high narrow ridge, and the Soil, Stony, Sandy and sufficently porous to drink up rains falling in the common way. And tho’ the Stream seems to have continued some time, certainly at least a few minutes, it nevertheless fell invariably in the same Spot, without moving to the right or left. I should be happy in having your opinion on this matter, my own Conjecture is that a Great Quantity of the Electric fluid, passing silently from the Cloud to the Mountain, carried the forming drops of rain from all quarters of the Cloud to one point, and by uniting them producd this prodigious Cataract—
I am, Dr. Sir, with the utmost respect and esteem, your sincere friend and most obedient humble Servant
Addressed: To His Excellency Benjamin Franklin Esqr. / Minister Plenipotentiary from the / United States to the Court of Versailles / Favor’d by Dr. Foulke
2. Later accounts of the “singular mountain freshet” recorded that the torrent had flooded the valley floor, depositing rocks and trees from the mountainside and causing extensive damage to livestock and dwellings. A bolt of lightning struck a tree in such a peculiar way that later Rittenhouse reportedly brought BF to see it. Rev. Conway P. Wing et al., History of Cumberland County, Pennsylvania, 1731–1879 (Philadelphia, 1879), pp. 114–15, 271.