Benjamin Franklin Papers

Account of Dr. Priestley’s New Experiments, [10 March 1768]

Account of Dr. Priestley’s New Experiments9

Autograph abstract: The Royal Society

[March 10, 1768].

A brief Account of that Part of Doctor Priestly’s Work on Electricity, which relates the new Experiments made by himself. This Part is divided into thirteen Sections.1

Section I. contains Experiments on the Excitation of Glass Tubes fill’d with compress’d Air, whereby he discover’d that the compress’d Air, does not, as had before been thought, prevent the Excitation, provided the Glass be warmed.

Section II. contains a Number of new and curious Experiments to prove that a Current of real Air proceeds from the Points of Bodies electrified either positively or negatively, which had been deny’d or disputed by some preceding Electricians.

Sect. III. contains Experiments on Mephitic Air, and on Charcoal. By the latter the Doctor discover’d a Property that was not before conceived to be in that Substance, viz. that it is, equally with Metals, a good Conductor of Electricity. Wood is, in its common State, but an indifferent Conductor, and when perfectly dry it was known not to conduct at all. Therefore, as all Water was suppos’d to be expell’d from it when reduc’d to Coal, it was not suspected that Charcoal would become a better Conductor than moist Wood; but the Doctor found it would perform the Office of the best Conductors, in conveying a Shock of the Leyden Bottle.

Sect. IV. contains Experiments on the conducting Power of various other Substances, viz. Ice, hot Glass, hot baked Wood, the Effluvia of flaming Bodies, melted Tallow, Oil of Olives, essential Oils of various Sorts, saline Substances of various kinds, black Sand, black Lead (which was unexpectedly found equally a good Conductor with Metal or Charcoal) various Stony Substances, Spars, &c. which afford a Number of Observations that are new and curious.

Sect. V. contains Experiments on the Diffusion of Electricity over the Surface of Glass Tubes, and showing a new Method of giving the electric Shock. These Experiments were partly made on new Flint Glass, which was found to differ greatly from Glass some Months old in regard to that Property ascrib’d to Glass of its being absolutely a Non Conductor. The Experiments are many and varied very ingeniously, particularly those relating to the new Method of giving a Shock, and tend to throw new Light on this Part of the Science.

Sect. VI. contains a Number of Experiments tending to verify several Particulars of P. Beccaria’s Theory concerning the electric Matter carrying into its Path light Substances to assist its Passage.2 To which are added sundry ingenious Experiments to discover if possible the Direction of the electric Fluid in an Explosion.

Sect. VII. contains various Experiments relating to charging and discharging Glass Jarrs, and Batteries. In these Experiments the Doctor appears to have raised and applied, at a considerable Expence of Time and Money, a much greater Force of Electricity than any one had done before him; and the Observations that arise on the Use of that Force in several Instances are very curious and useful.

Sect. VIII. contains Experiments on Animals struck by these powerful Discharges; and gives a particular Account of the Effects and Appearances upon them while they were dying and after their Death. Animals larger and more difficult to kill, appear to have been killed by the Doctor’s Apparatus, than by any other before used; and the Facts and Circumstances are in several of the Instances very surprizing.

Sect. IX. contains Experiments on the circular Spots made on Pieces of polish’d Metal by large electrical Explosions. Three concentric Circles were sometimes made by one Explosion.3 From this Experiment the Doctor endeavours to explain some extraordinary Effects of Lightning, and particularly what are called the Fairy Rings.

Sect. X. contains Experiments on the Effects of the electric Explosion discharged thro’ a brass Chain and other metallic Substances. A black Smoke or Dust was found to be constantly thrown off from the Chain upon the Paper on which it lay, so as to mark the Paper strongly with a black Stain distinguishing the Links. This seems a Fact very curious, as are the Observations made by the Doctor upon it, and the subsequent Experiments he made in pursuance of it.

Sect. XI. contains new Experiments on the Passage of the Electric Explosion over the Surface of some conducting Substances without entring them.

Sect. XII contains new Experiments on the Tourmalin;4 and

Sect. XIII contains a number of miscellaneous Experiments, all very curious with regard both to the Views with which they were made, and the Success of the several Variations in making them.

Upon the whole Dr. Priestly appears to be a very intelligent, ingenious, and indefatigably diligent Experimenter; and to have contributed considerable Materials for the Improvement of the Electrical Branch of Natural Philosophy.

Endorsed: Read March 10 1768.

Not to be printed

[Note numbering follows the Franklin Papers source.]

9A paper by BF read to the Royal Society at its meeting on March 10, 1768, and preserved in its archives; see Robert E. Schofield, A Scientific Autobiography of Joseph Priestley (1733–1804) (Cambridge, Mass., [1966]), p. 335. BF’s purpose in his paper was to carry on the campaign begun the previous autumn to have Priestley awarded the Copley Medal; see above, XIV, 311, 326–8.

1“New Experiments in Electricity, made in the year 1766,” in Joseph Priestley, The History and Present State of Electricity, with Original Experiments … (London, 1767), pp. 573–733.

2For Giambatista Beccaria and Priestley’s admiration for his work see above, V, 395 n.

3A paper by Priestley on this subject was read at the same meeting of the Royal Society; see the preceding document.

4Eighteenth-century experimenters, Priestley included, were interested in tourmaline because of its property of generating an electrical charge when heated.

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