Passages for Priestley’s History of Electricity
Drafts: American Philosophical Society
As other documents in this volume show, Franklin was one of several friends who read sections of Joseph Priestley’s History of Electricity while it was in preparation during 1766, offered information and suggestions, and on occasion submitted revised or expanded phraseology at various points. Among Franklin’s surviving papers are two sheets containing passages in his hand which appear largely unchanged in Priestley’s printed work. These papers contain cancellations and revisions themselves and are obviously drafts of suggested new or expanded phraseology that Franklin sent to Priestley and that the latter gratefully accepted, revised slightly, and then incorporated in the book.
The first passage appears in two parts in the History of Electricity. The first part of this passage, as far as the word “backwards,” forms a short paragraph near the bottom of page 50. The second part becomes a paragraph near the top of page 51. The second and somewhat longer passage occupies almost the whole of page 424. Notes are appended here to indicate the changes Priestley made in each of Franklin’s contributions.
The Doctrine of two different Electricities produc’d by exciting different Substances and of their Effects on each other7 seems to have been dropt after Monsr. Dufay8—and those Effects ascrib’d to other Causes; which is an Instance that Science sometimes goes backwards. Many Years after, Mr. Kinnersley,9 a Friend of Dr. Franklin’s, being at Boston in New England, made some Experiments which again show’d that Difference of Electricities.1 He communicated those Experiments to Dr. Franklin, who repeated and explain’d them. See Franklin’s Letters.2
It ought to be so on Dr. F.’s Principles.3 If one Side be rubbed by the Finger; it acquires from the Finger some of the Electric Fluid. This being spread on the Glass as far as the Rubbing extended, repels an equal Quantity of that contain’d in the other Side of the Glass, and drives it out on that Side, where it stands as an Atmosphere, and so4 both sides are found plus. If the unrubb’d Side were in Contact with a Conductor communicating with the Earth, the Electric Fluid would be carried away, and then that Side would be left apparently in the natural State. If the electric Fluid found on the unrubb’d Side was really part of that which had been communicated by and from the Finger, and so had actually perm[eated] the Glass, it might, when conducted away, be continually replac’d by fresh permeating Fluid communicated in the same Manner: But if the Effect is continually diminishing, while the suppos’d Cause repeated, continues the same, there seems reason to [doubt] the Relation5 between that Cause and the Effect. It appears difficult to conceive how Electric Fluid having pass’d thro’ a permeable Body, should make it more difficult for other Electric Fluid to follow, till at length none would pass thro’ at all.6
7. In the place of the seven words following “Substances,” Priestley wrote: “considerable as the discovery of it was.”
8. See above, IV, 423.
9. Priestley: “It will be seen that, many years after, Mr. Kinnersley of Philadelphia,” etc.
1. Priestley: “of the two electricities.”
2. Above, IV, 263–4, 275–6. These last words appear in Priestley as a footnote: “See his Letters.” At a blank corner of this paper BF wrote in a different ink for some purpose unknown: “Devonshire Street Bishopgate street.”
3. Priestley: “upon this I cannot help observing that it ought to be so on Dr. Franklin’s principles.”
4. Priestley: “so that.”
5. Priestley: “the supposed relation.”
6. Priestley revised the final sentence to read: “For it appears difficult to conceive how some electric fluid, having passed through a permeable body, should make it more difficult for other particles of the same electric fluid to follow, till, at length, none could pass at all.”