Benjamin Franklin Papers

To Benjamin Franklin from Thomas Ronayne with Notes for a Reply, 26 August 1761

From Thomas Ronayne1 with Notes for a Reply

ALS: American Philosophical Society

Corke August the 26th. 1761.


I beg Leave to Communicate to you a few Experiments and observations on Electricity, both common and atmostpherical, and to have your opinion of them.

It seems to me that Electricks per Se or Non Conductors do not contain more of the Elctrick Fluid than Non Electricks.2 For An Insulated Wire being heated at one end, and having Light threads hanging from any Part of it did not shew the Least sign of being Electrified when a Stick of wax was applied to the heated part of the wire; tho’ wax becomes non Electrick by melting: Neither did an In[s]ulated Wire shew any Sign of Electricity after a Piece of Melted Glass coold on it; tho’ (According to Mr. Willson3) melted Glass is non electrick.

The Expansion, or contracktion of a body Seems not to Electrifie it for a Wire put in an open thermometer of Spirit of Wine, non electrick; or oil of Turpentine an electrick per se; Shew’d no Sign of electricity either when the Liquor contracted or expanded. The Air in a Room may be electrified either positively or negatively by applying either the hook or coating of a charg’d Phial to one end of an insulated Wire sharp Pointed at the other end.

The Electricity of the Air shews itself only by causing cork balls hung in contact, or threads, to repell each other. In a frost, in a fog, and sometimes in a Mist with small Rain I have found the Air without Doors to be electrified, and even in a frosty Night tho there was no Aurora Borealis; in all these Cases the Electricity was positive. When the Summer came I never could find the Air to be electrified except from Thunder or Showers and then the Electricity was sometimes negative, and sometimes positive. And was much Stronger than that in the winter. We had two Thunder Storms this Summer. In the 1st. I try’d Mr. Cantons curious Electrometer Described Phil: Transac. Vol 48 Part 2d. No 934 which I allways carry in my Pocket along with a stick of sealing wax and another of Glass but the wind agitated the Cork Balls in such a manner that I could not satisfie my self; which is an inconvenience I know not how to remedy.5

The Next day I satisfied mySelf both by the Electrometer and by holding a Pole round which a Wire was twisted while I Stood on wax. There were changes from negative to positive and from that to negative and lastly to positive.

Queries concerning Thunder

How do the Clouds or Air become electrified? Why is the Electricity of the Clouds so Strong; when that of the Air is so weak.

Why does not the Electrick Fire in or about a Cloud dissipate it; or at Least hinder it from Raining? Was Rain Water caught in an electrick per se ever found to be electrified? Is a Cloud electrized more in Proportion than any other body? Were Light bodies ever observ’d to be attracted towards an Electrified Cloud?

What is the Cause of the continued length of a Clap of Thunder? Can Fire balls and other Phoenomena seen with or without Lightning be accounted for by electrical Principles? In haste I am with Sincere respect, Your Most obliged humble Servant

Thos. Ronayne

Addressed: To / Benjamin Franklin Esqr. / of / Philadelphia

[On another page in Franklin’s hand in red ink:]

The Balls may be kept from the Wind by hanging them from the Cork within a thin Glass Phial; where they will nevertheless be affected by the State of Electricity in the Air.

Rain water, caught during a Thundershower, has been found to be electrified.

Small Fragments of Cloud are often seen to be attracted to the large Body of Cloud of a Thunder Gust. The Leaves on the Tops of Trees are observ’d to be drawn up wards when the Great Cloud first comes over them, and the Dust is also drawn up.

A number of Strokes from Cloud to Cloud, though all at the same Instant, will give Sounds that arrive at the Ear in Succession according to the different Distances.

1Thomas Ronayne (d. c. 1800), scion of an old Irish family, probably acquired his interest in science from his father Philip Ronayne (c. 1683–1755), a friend and correspondent of Newton. Interested in “atmospheric Electricity,” the son began “experiments on the Air” in 1761 and “those on the Clouds” in 1762. Journal of the Cork Hist. and Archaeol. Soc., second series, XXIII (1917), 99–104. While BF’s full reply to this letter has not been found, they corresponded further in 1766 and 1772.

2To understand Ronayne’s experiments it should be remembered that at this time the term “electrick per se” was commonly used for a substance (such as glass or wax) which in its normal state could store an electric charge but not transmit it, and “non electrick” for one (such as copper) which transmitted it but seemingly could not store it.

3For Benjamin Wilson, electrician and portrait painter, see above, IV, 391 n; VIII, 239–63.

4Canton’s “Electrometer” was a “small narrow box with a sliding cover” inside of which was a pair of pea-sized cork or elder balls attached to a wire “by linen threads of six inches long.” The cover being pulled back and the balls being permitted to dangle in the air, they could by their attraction or repulsion determine the nature of the charge in the atmosphere. John Canton, “A Letter to the Right Honourable the Earl of Macclesfield … concerning some new electrical Experiments,” Phil. Trans., XLVIII (1754), 780–5.

5The italicized words, here and in the queries below, are lightly underlined in the MS. Perhaps BF, not Ronayne, did this in preparation for drafting the notes of a reply which are here printed at the end of Ronayne’s letter.

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