“Farther, if the wire with its loose threads was reverted, so as to encompass the lower part of the cylinder (as before it did the upper part) yet the effect still answered with the same exactness. For the threads were all erected into so many strait lines, still directing themselves towards a center in the axis of the glass.
“Hitherto the axis of the cylinder was placed horizontally; in the next place I set it in a vertical position, so that it stood perpendicular to the plane of the horizon; in which case I made use of a wire hoop, which was necessary to be placed parallel to the horizon, that it might encompass the cylinder, in the same manner as the semicircular wire did before: only one small part of this wire was left open, to make way for the touch of the hand, which was to give the attrition. And the wire being thus placed, it was evident that the threads (without some external force to support them) must all flag and hang perpendicularly downwards. Yet, as soon as the motion and attrition were given, the threads presently began to be extended; and as if they were become stiff and hard, formed themselves into an horizontal plane; their loose ends pointing to a center in the axis of the glass, as before.
“And thus (in all sorts of positions whatsoever, both of the wire and of the glass too) were the threads acted upon by a sort of centripetal force; to the laws of which they were always conformable.” See Hauksbee’s experiments, page 53 &c.
It may be observed in this experiment, that the attractive power of bodies does not lie in solids, as has been falsly imagined, neither have such bodies any centripetal or centrifugal force; but that this power and force are given them from without. For, on placing the wire with the threads round the cylinder, they were all forced (or as it is often called, attracted) towards the earth; but, on giving a violent motion to the cylinder, they were drove from the cylinder, as if forced by a strong wind; but, by applying the hand to the glass cylinder, they were recalled, and all pointed to a center in the axis of the cylinder: and this central direction might be altered at any time, by only moving the hand to different parts of the cylinder; the threads always pointing to the place where the attrition was made: by which we find, that the central force, both of the cylinder and the threads, are caused by the attrition of the air between your hand and the cylinder; whereas, at any other time, they are quite inactive: so we are assured that these central forces which have been imagined to be within the solid, are not there, but in the air without it.
On putting something between any of the threads and the cylinder; then, those threads would return to their first and natural position, viz. point towards the center of the earth. So, as Mr. Hauksbee observes, “in these small orbs of matter we have some little resemblances of the grand phænomena of the universe.”
Another thing observable was, “that by putting these threads within a glass, when they became extended, this position of the threads would be altered at any time on the approach of one’s hand, finger, or any other body, to the surface of the glass.” This is sufficient proof that the light, or as it is generally called, the electrical effluvia pass through the glass, with as much ease as water does through a sieve.
One thing which seemed a little surprising to Mr. Hauksbee was, that upon exhausting the gross air out of the tube or globe made use of in electricity, what he called the power of attraction, would cease; but upon suffering the air again to enter, it returned as vigorous as before. This must be the case; for (as was before observed) whenever the gross air is extracted by an air pump, the fluid remaining is nothing but light. So, whenever this attrition is performed on an exhausted globe (for want of the resistance of the gross air within, to force off the particles of air ground so small as light, and thereby to make an expansion or rarefaction round the glass globe, which has been shewn to be the cause of light bodies being forced towards the globe) these particles of light do immediately enter the globe on one side, and force out the same quantity on the other; in the same manner as water through a sieve, without ever making any expansion or rarefaction.
Having thus shewn how and by what means the fire and light in electricity are produced; our next inquiry must be, why some bodies communicate this light to ever so great a distance, and that instantaneously; whilst others will not; and also, why some bodies are electrical and others non-electrical.
Electrical bodies are those, whose pores are so fine, as to admit nothing through them but light, or air ground to a proper fitness; as metalls, glass, amber, wax &c. Bodies non-electrical, are all those, which, by the largeness of their pores, admit, not only light but also gross air.
We see, when the air is ground to pieces by an electrical machine, and put into sufficient motion, by the friction between the glass globe and the hand, a wire being hung from the iron barrel, so as very near to touch the ball, part of the light issuing from the ball, as above described, enters the wire, and is by it communicated to the iron barrel, and from thence carried by another wire to any distance, if not interrupted by some non-electrical body: to the end of which, by a third wire is hung an egg; as soon as the globe is put in motion, and warm spirit of wine is placed so as to touch the egg, the spirit of wine will immediately take fire from the contact of the egg.