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I have made several Trials in order to fire Gunpowder alone, which I tried both warm and cold, whole and powder'd, but never could make it succeed; and this arises in part from its Vapours not being inflammable, and in part from its not being capable of being fir'd by Flame, unless the Sulphur in the Composition is nearly in the State of Accension. This we see by putting Gunpowder into a Spoon with rectified Spirit, which, when lighted, will not fire the Powder, 'till by the Heat of the Spoon from the burning Spirit, the Sulphur is almost melted. Likewise, if you hold Gunpowder ground very fine in a Spoon over a lighted Candle, or any other Flame, as soon as the Spoon is hot enough to melt the Sulphur, you see a blue Flame, and instantly the Powder flashes off. The same Effects are observ'd in the Pulvis fulminans, compos'd of Nitre, Sulphur, and fixed Alkaline Salt. Besides, when the Gunpowder is very dry and ground very fine, it (as you please to make the Experiment) is either attracted, or repell'd; so that in the first Case, the End of your Finger when electrified, shall be cover'd over with the Powder, though held at some Distance; and in the other, if you electrify the Powder, it will fly off at the Approach of any non-electrified Substance, and sometimes even without it. But I can at Pleasure fire Gunpowder, and even discharge a Musket, by the Power of Electricity, when the Gunpowder has been ground with a little Camphor or with a few Drops of some inflammable chemical Oil. This Oil somewhat moistens the Powder, and prevents its flying away; the Gunpowder then being warm'd in a Spoon, the electrical Flashes fire the inflammable Vapour, which fires the Gunpowder: But the Time between the Vapour firing the Powder is so short, that frequently they appear as the same and not successive Operations, wherein the Gunpowder itself seems fired by the Electricity; and indeed the first Time this Experiment succeeded, the Flash was so sudden and unexpected, that the Hand of my Assistant, who touch'd the Spoon with his Finger, was considerably scorch'd. So that there seems a fourth Ingredient necessary to make Gunpowder readily take Fire by Flame, and that such a one, as will heighten the Inflammability of the Sulphur. In common Cases the lighted Match or the little Portion of red hot Glass, which falls among the Powder, and is the Result of the Collision from the Flint and Steel, fires the Charcoal and Sulphur, and these the Nitre. But if to these three Ingredients you add a fourth, viz. a Vegetable chemical Oil, and gently warm this Mixture, the Oil by the Warmth mixes intimately with the Sulphur, lowers its Consistence, and makes it readily take fire by Flame. In these Operations, notwithstanding I always made use of the finest scented Oils of Orange Peel, Lemons, and such like, yet upon the least warming the Mixture, the rank Smell of Balsam (i. e. the ready Solution) of Sulphur was very obvious.
Read before the R. S.Oct. 24. 1745.
A Continuation of the Above
Read, Feb. 6. 1745.
As Water is a non-electric, and of Consequence a Conductor of Electricity, I had Reason to believe that Ice was endowed with the same Properties. Upon making the Experiment I found my Conjectures not without Foundation; for upon electrifying a Piece of Ice, wherever the Ice was touched by a non-electric, it flashed and snapped. A Piece of Ice also held in the Hand of an electrified Man, as in the beforementioned Processes, fired warm Spirit, chemical vegetable Oils, Camphor, and Gunpowder prepared as before. But here great Care must be taken, that by the Warmth of the Hand, or of the Air in the Room, the Ice does not melt; if so, every Drop of Water therefrom considerably diminishes the received Electricity. In Order to obviate this, I caused my Assistant, while he was electrifying, to be continually wiping the Ice dry upon a Napkin hung to the Buttons of his Coat, and this being electrified as well as the Ice, prevented any Loss of the Force of the Electricity. The Experiment will succeed likewise, if, instead of the Ice, you electrify the Spirit, &c. and bring the Ice not electrified near them. I must observe, that Ice is not so ready a Conductor of Electricity as Water; so that I very frequently have been disappointed in endeavouring with it to fire inflammable Substances, when it has been readily done by a Sword or the Finger of a Man.
In the first Paper3 I had the Honour to lay before you upon this Subject, I took Notice of my having observed two different Appearances of the Fire from electrified Substances; viz. those large bright Flashes, which may be procured from any Part of electrified Bodies, by bringing a Non-Electric unexcited near them, and with which we have fired all the inflammable Substances mentioned in the Course of these Observations; and those, like the firing of wet Gunpowder, which are only perceptible at the Points or Edges of excited Non-electrics. These last also appear different in Colour and Form according to the Substances from which they proceed: For from polished Bodies, as the Point of a Sword, a Silver Probe, the Points of Scissors, and the Edges of the Steel-bar made Magnetical by the ingenious Dr. Knight, the electrical Fire appears like a Pencil of Rays, agreeing in Colour with the Fire from Boyle's Phosphorus; but from unpolished Bodies, as the End of a Poker, a rusty Nail or such-like, the Rays are much more red. The Difference of Colour here, I am of Opinion, is owing rather to the different Reflection of the electrical Fire from the Surface of the Body from which it is emitted, than to any Difference in the Fire itself. These Pencils of Rays issue successively as long as the Bodies, from which they proceed, are exciting; but they are longer and more brilliant, if you bring any Non-Electric not excited near them, though it must not be close enough to make them snap. If you hold your Hand at about two or three Inches Distance from these Points, you not only feel successive Blasts of Wind from them, but hear also a crackling Noise. Where there are several Points, you observe at the same Time several Pencils of Rays.
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It appears from Experiments, that besides the several Properties, that Electricity is possess'd of peculiar to itself, it has some in common with Magnetism and Light.
