From Thomas Ronayne2
ALS: American Philosophical Society
Corke (in Ireland) October 22. 1766
[Illegible] of last July I received your kind Letter bearing date of April 20th.3 together with your Book of Whirlwinds, Waterspouts, &c.4 which I should have acknowledg’d before now but that I was in daily Expectation of having opportunities for offering these Remarks.
As to what you observe how any large body electrified may cause smaller ones to be electrified the Reverse of what itself is, that might have often been the case when I had a Tin Tube which did not end in a sharp Point but the one I describ’d to you does, beside I made observations of several changes from Negative to positive and viceversa when I stood on a cake of Wax with a Pole in my hand round which a Wire* was twisted during the passing of what seem’d one Cloud and that not very extensive, so that if there was a succession of Clouds the Electricity of each must have been very great.
I have read your experiments in pursuance of those of Mr. Canton.5 They together with your ingenious Conjectures in your letter shew how in some circumstances the Electricity may be changed in contrarium when the Lightning strikes to the Earth without supposing Electricity in the Earth to be the cause of Thunder as Beccaria Seems to think.6
I have since discoverd that the Reason why Electrical Experiments do not succeed in damp weather is owing to Silk imbibing Moisture from the Air; for bodies insulated by Sealing Wax or gum lac7 retain Electricity very well at all times, and the Moistest Air conducts very slowly as I found by Electrifing it in a Room.
I also discover’d that Silk dryed and dipt in [illegible] melted, if kept in ones pocket is convenient to have [in rea]diness, but the best way of insulating bodies is thus, [torn] a Piece of Sealing Wax, or Gum lac at each end making a hole transversely through which you may put Silk, or even Twine. With two pieces in this manner a prime Conductor can be insulated.
I should have mentiond an Experiment favouring your principles, Viz. Let a pair of Cork balls suspended by dry silk be electrified by Glass, or wax, approach them with the Same and it will never close them; so that the cause of the encrease or decrease of repulsion is not the Different density of internal and external Electricks Fluid, but what you said.
In a letter I wrote to you before I receivd your letter I conjecturd that Vapour, or a Cloud when electrified is more or less capable of exploding as ’tis more or less compress’d, this follows from your principles as it doth that Vapour can receive more Electricity than the same quantity converted into Water, therefore some Part of a Cloud may conduct much better than others at the same time; this perhaps may account for the changes during the Passing of what seems one Cloud or Nimbus, it may also serve to shew that when the Electricity upon a Flash appears and disappears the Equilibrium of any Cloud with the Earth may not be restor’d, and explain several Phenomena in Lightning, and variations in the Noise of Thunder; but I cannot to much recommend the Signals &c.
The foremost Clouds of a Shower &c. are generally Negative. In a Shower of Snow the Electricity tho on and of[f] at different times yet was always Negative, till after the Shower was just past there was a weak positive Electricity, discoverable only by Mr. Cantons Electrometer.8 In haste I am Most excellent Sir Your most obedient humble Servant
P.S. I attempted the Experiment I mentiond to you of the Wax to try whether hot Air at the Surface is what only makes Electricks per se seem conductors or not; the Experiment seem’d to favour the Affirmative tho not so small a Quantity of Wax would not keep in such perfect fusion as I could wish.
Addressed: To / Benjamin Franklin Esqr / Cravenstreet, Strand / London9
2. On Ronayne see above, IX, 350 n.
3. Above, pp. 247–50.
4. Presumably BF had sent an offprint of his “Physical and Meteorological Observations, Conjectures, and Suppositions” that had been published in Phil. Trans., lv (1765), 182–92.
5. Above, V, 516–19.
6. For this theory and BF’s belief that it might, at least sometimes, be valid, see above, V, 396, 428.
7. Gum lac is one variety of a resinous incrustation (called lac) deposited on twigs of various trees in India and other parts of southern Asia by an insect known variously as Tachardia lacca or Carteria lacca. The shellac of commerce is a refined and processed form of lac.
8. For this device, see above, IX, 351 n.
9. On the address page appears a series of financial calculations, apparently in BF’s hand, involving sums in the hundreds of pounds. Their purpose or significance cannot be determined.