A Letter from - to Mr. John Ellicot, F. R. S. of Weighing the Strength of Electrical Effluvia

A represents a thin Piece of Sponge, so cut as to contain as large a Superficies as possible. This hangs by a fine Thread of Silk, upon the Beam B, and is exactly balanced by another Thread of Silk at D, strung with the smallest Lead-Shot, at equal Distances, and so adjusted as to cause the Index E to point at G, in the Middle of the graduated Arch F, G, H, when the Air is in a middle State between the greatest Moisture and the greatest Dryness. I. shews a little Table or Shelf, for that Part of the Silk and Shot which is not suspended, to rest upon. More Words are, I believe, unnecessary; and therefore I only beg you'll believe me, Yours, &c, Feb. 15. 1745. W. Arderon. II. A Letter from ———— to Mr. John Elliotcot, F. R. S. of weighing the Strength of Electrical Effluvia. SIR, Read March 6. 1745-6. As you were the first, and indeed the only Person who ever shew'd me any electrical Experiments, and have been so kind, according to your wonted Candour, to assist me freely upon this and all other like Occasions; I think it proper to give you this first Account of what I have thought thought of towards gaining a farther Insight into the Nature, Power, and Laws of Electricity. From the Time I saw those Experiments at your House about 3 Years ago, I had little or no Opportunity of making any myself, until within this Month; when, having got some good Utensils, I repeated or imitated most of the Trials I had heard of, with Success. And particularly having heard, that Mr. Gray gave an Account of Balls caused to move round one another by means of electrical Effluvia, I was very desirous of seeing so delightful a Sight *. And though I was disappointed in my Expectation of a circular Motion, yet I found it easy to make two Balis act upon each other, in a very entertaining Manner, for a long time; and that with such a Constancy and Regularity, as to the Effect, that I apprehend one may thence deduce a Gauge or Standard, whereby to measure electrical Powers, and compare the Quantities and Strength of the Virtue infused into, or remaining in, non-electrical Bodies after given Times, &c. This, together with a great Desire to be able to estimate and compare the Effects of Experiments with some Certainty, and to do something more than amuse myself and Friends with the several surprising Phenomena which those Experiments produce, led me, about 10 Days ago, to think of a Method, which, for aught I know, is quite new, and seems to promise fair to afford much new Light: It is to try or weigh * See Phil. Trans. n. 441, p. 220. & n. 444, p. 400. weigh the Strength of the electrical Effluvia, Virtue, or Power, by causing it to act upon a Balance. I found, the first Day, that this Method answered even beyond my Expectation; so that several non-electrical Balls placed successively underneath one of the Scales, and then imbued with electrical Virtue the common Way, would presently cause that Scale to descend two, three, four, or five Inches, and seem to cleave, for 10 or more Seconds of Time to the several Bodies so placed underneath, some having much greater Effect than others. Whence it appeared, that there was a sufficient Latitude for comparing very different Forces, if any such there were. At the next and only Opportunity I have had since (my Apparatus being made more commodious), I used flat instead of globular Bodies, and then I found the Effects far more considerable; some of them, whose upper Surface was about 3 Inches square, having attracted and held down one Scale, when there were about 200 Grains Weight in the other. Though I am tempted to communicate some Things, which I have already observed by this means, with much Delight, I reserve them at present for a farther Examination; desiring in the mean time, that you will communicate or divulge this in such manner as you think proper (only concealing my Name), that others, who may have an Inclination, may pursue and improve the Hint. And, for the Ease of such, I must add, that the Strings of that Scale which is to be acted on, must be long, and non-electrical, and, I think, thick; that there may be a ready Passage for the electrical Virtue to run off, as fast as it is received. Instead of a brass Scale-pan, I used a flat Piece of Cork, filed very smooth and even, especially on the under Surface. The other Scale needs no Alteration, provided the Strings be made of Silk, as usual, and short enough to keep that Scale out of the Reach of the electric Virtue, which is to act upon the former. If the Beam were three or four Feet long, the Strings of both Scales might be of a Length, which would make it less troublesome to put in and take out Weights. I mounted the attracting Bodies upon small taper Sticks about two Feet and an half long, whose thicker Ends had a Foot which stood upon two Cakes of Bees-Wax full 10 Inches thick in all. I forbear to describe the pretty little simple Instrument you furnished me with at my first setting out; I leave that to yourself; only, as it has no Name, I take the Liberty to call it An Electrical Needle. Every body, who delights in such Matters, will thank you for it, if it were only for the Amusement it will furnish for so many Hours, after being but once well seasoned or tinctured with electrical Effluvia. But, I think, this little Instrument, and the Balance together, cannot fail of informing us farther concerning the Properties of Electricity: Such as, how far it agrees and disagrees with Magnetism; whether it passes through the Substance, or only along the Surface of Bodies; whether it proceeds in any, and what, particular Direction, or has any particular Tendency; in what particular Bodies the most of it may be collected and retained; and how long; how far the Figure, Size, Density, or Colour of Bodies may be concerned; whether, as these Effluvia may be felt, heard and seen, they may likewise be weighed; and many other Matters, which will occur to the diligent Observer. Your humble Servant. III.