Читать книгу Experiments and Observations Tending to Illustrate the Nature and Properties of Electricity - William Watson - Страница 2
TO Martin Folkes, Esq;
P. R. S
ОглавлениеSIR,
THE Society having heard from some of their Correspondents in Germany, that what they call a Vegetable Quintessence had been fired by Electricity, I take this Opportunity to acquaint you, that on Friday Evening last I succeeded, after having been disappointed in many Attempts, in setting Spirits of Wine on Fire by that Power. The preceding Part of the Week had been remarkably warm, and the Air very dry, than which nothing is more necessary towards the Success of Electrical Trials; to these I may add, that the Wind was then Easterly and inclining to freeze. I that Evening used a glass Sphere as well as a Tube; but I always find myself capable of sending forth much more Fire from the Tube than from the Sphere, probably from not being sufficiently used to the last.
I had before observ'd, that although2 Non-electric Bodies made electrical, lose almost all that Electricity by coming either within or near the Contact of Non-electrics not made electrical; it happens otherwise with Regard to Electrics per se, when excited by rubbing, patting, &c; because from the rubbed Tube I can sometimes procure five or six Flashes from different Parts, as though the Tube of two Foot long, instead of being one continued Cylinder, consisted of five or six separate Segments of Cylinders, each of which gave out its Electricity at a different Explosion.
The Knowledge of this Theorem is of the utmost Consequence towards the Success of electrical Experiments; inasmuch as you must endeavour by all possible Means to collect the Whole of this Fire at the same Time. Professor Hollman seems to have endeavour'd at this and succeeded, by having a tin Tube, in one End of which he put a great many Threads, whose Extremities touch'd the Sphere when in Motion, and each Thread collected a Quantity of electrical Fire, the Whole of which center'd in the tin Tube, and went off at the other Extremity. Another Thing to be observ'd, is to endeavour to make the Flashes follow each other so fast, as that a Second may be visible before the First is extinguish'd. When you transmit the electrical Fire along a Sword or other Instrument, whose Point is sharp, it often appears as a Number of disseminated Sparks, like wet Gunpowder or Wild-fire; but if the Instrument has no Point, you generally perceive a pure bright Flame, like what is vulgarly call'd the Blue-ball, which gives the Appearance of Stars to fired Rockets.
The following is the Method I made use of and was happy enough to succeed in. I suspended a Poker in silk Lines; at the Handle of which I hung several little Bundles of white Thread, the Extremities of which were about a Foot at right Angles from the Poker. Among these Threads, which were all attracted by the rubbed Tube, I excited the greatest electrical Fire I was capable, whilst an Assistant near the End of the Poker held in his Hand a Spoon, in which were the warm Spirits. Thus the Thread communicated the Electricity to the Poker, and the Spirit was fired at the other End. It must be observ'd in this Experiment, that the Spoon with the Spirit must not touch the Poker; if it does, the Electricity without any flashing is communicated to the Spoon, and to the Assistant in whose Hand it is held, and so is lost in the Floor.
By these Means, I fired several Times not only the ætherial Liquor or Phlogiston of Frobenius and rectified Spirit of Wine, but even common proof Spirit. These Experiments, as I before observ'd, were made last Friday Night, the Air being perfectly dry. Sunday proved wet and Monday somewhat warm, so that the Air was full of Vapour; Wind South-West and cloudy. Under these Disadvantages, on Monday Night I attempted again my Experiments; they succeeded, but with infinitely more Labour than the preceeding, because of the Unfitness of the Evening for such Trials. Your Candour will not permit you to think my Minuteness trivial, with Regard to the Circumstances of the Weather, who know, how many Things must concur to make these Experiments succeed. I shall wait with Impatience for a proper Opportunity to have these Experiments repeated in your Presence, and am, with the utmost Respect,
Sir, your most obedient,
humble Servant,
W. Watson.
Aldersgate-Street,
March 27. 1746.
2
I call Electrics per se or originally-electrics, those Bodies, in which an attractive Power towards light Substances is easily excited by Friction; such as Glass, Amber, Sulphur, Sealing-wax, and most dry Parts of Animals, as Silk, Hair, and such like. I call Non-electrics or Conductors of Electricity, those Bodies, in which the above Property is not at all or very slightly perceptible; such as Wood, Animals living or dead, Metals and vegetable Substances. See Gray, Du Fay, Desaguliers, Wheler, in the Philosophical Transactions.
