Queries from Dr. Ingenhouse, with my Answers, BF; Question I.

If the electrical Fluid is truly accumulated on the Inside of a Leiden Phial, and expelled in the same Proportion from the other side, why are the Particles of Glass not all thrown outwards when the Phial, being over-charged, breaks or is perforated by a spontaneous Explosion? Answer

By the Circumstances that have appear’d to me, in all the Jarrs that I have seen perforated at the Time of their Explosion, I have imagined that the Charge did not pass by those Perforations. Several single Jarrs that have broke while I was charging them, have shown, besides the Perforation in the Body, a Trace on both sides the Neck, wherein the Polish of the Glass was taken off, the Breadth of a Straw; which prov’d that great Part at least, of the Charge, probably all, had passed over that Trace. I was once present at the Discharge of a Battery containing 30 Jarrs, of which 8 were perforated and spoilt at the Time of the Discharge, yet the Effect of the Charge on the Bodies upon which it was intended to operate, did not appear to be diminished. Another Time I was present when twelve out of Twenty Jarrs were broken at the Time of the Discharge, yet the Effect of the Charge which pass’d in the regular Circuit, was the same as it would have been if they had remained whole. Were those Perforations an Effect of the Charge within the Jarr forcing itself thro’ the Glass to get at the Outside, other Difficulties would arise and demand Explanation, 1. How it happens that in 8 Bottles and in 12 the Strength to bear a strong Charge should be so equal, that no one of them would break before the rest and thereby save his Fellows; but all should burst at the same Instant? 2. How it happens that they bear the Force of the great Charge till the Instant that an easier Means of Discharge is offered them, which they make use of, and yet the Fluid breaks thro’ at the same time? My Conjecture is, that there has been in the Place where the Rupture happens, some Defect in the Glass, some Grain of Sand perhaps, or some little Bubble in the Substance, nearly void, where during the Charging of the Jarr the Electric Fluid is forc’d in and confin’d, till the Pressure is suddenly taken off by the Discharge, when not being able to escape so quickly, it bursts its way out by its elastic Force. Hence all the Ruptures happen nearly at the same Instant with the regular Discharge, tho’ really a little posterior, not being themselves Discharges, but the Effects of a Discharge which pass’d in another Channel. Question II

When a strong Explosion is directed through a Pack of Cards or a Book, having a Piece of Tinfoil between several of its Leaves, the Electrical Flash makes an Impression on some of those metalic Leaves, by which it seems as if the Direction of the electric Explosion had gone from the Outside towards the Inside, when on the other metallic Leaves, the Impression is in such a Direction that it indicates the Current of electrical Fire to have made its way from the Inside of the Phial towards the Outside; so that it appears to some Electricians, that in the time of the Explosion of an Electrical Phial, two Streams of electrical Fire rush at the same time from both Surfaces, and meet or cross one another. Answer

Those Impressions are not Effects of a moving Body, striking with Force in the Direction of its Motion; they are made by the Burs rising in the neighbouring perforated Cards, which rise accidentally sometimes on one Side of a Card, sometimes on the other in consequence of certain Circumstances in the Form of their Surfaces or Substances or Situations. In a single Card supported without touching others while perforated by the passing Fluid, the Bur generally rises on both Sides, as I once show’d to Mr Symmer at his House. I imagine that the Hole is made by a fine Thread of El. Fluid first passing, and augmented to a bigger Thread, at the Time of the Explosion, which obliging the Parts of the Card to recede every way, condenses a Part within the Substance, and forces a Part out on each side, because there is least Resistance. Question III.

When a Flash of Lightning happens to hit a flat Piece of Metal, the Metals has sometimes been pierced by several Holes, whose Edges were turned some the one way, and some the other, so that it has appeared to some Philosophers, that several Streams of Electrical Fire had rushed in one way, and some the opposite way. Such an Effect of Lightning has been published lately by Father Barletti.

This will be answer’d in my Remarks on M. Barletti’s Book which Remarks when finish’d I will send you. Question IV.

Though from the very Charging of the Leiden Phial it seems clear, that the electrical Fluid does in reality not pervade the Substance of Glass, yet it is still difficult to conceive how such a subtil Fluid may be forced out from one Side of a very thick Pane of Glass by a similar Quantity of electrical Fire thrown upon the other Surface, and yet that it does not pass through any Substance of Glass, however thin, without breaking it. Is there some other Fact or Illustration besides those to be found in your public Writings by which it may be made more obvious to our Understanding that electrical Fire does not enter at all the very substance of Glass, and yet may force from the opposite Surface an equal Quantity of; or, that it enters really the Pores of the Glass without breaking it? Is there any comparative Illustration or Example in Nature, by which it may be made clear, that a Fluid thrown upon one Surface of any Body may force out the same Fluid from the other Surface without passing through the Substance?

That the Electric Fluid by its repulsive Nature is capable of Forcing Portions of the same Fluid out of Bodies without entring them itself, appears from this Experiment. Approach an isolated Body with a rubb’d Tube of Glass; the Side next the Tube will then be electris’d negatively, the opposite positively. If a pair of Cork Balls hang from that opposite side, the Electrical Fluid forc’d out of the Body, will appear in those Balls, causing them to diverge. Touch that opposite Side, and you thereby take away the positive Electricity. Then Remove the Tube, and you leave the Body all in a negative State. Hence it appears that the Electric Fluid appertaining to the Glass Tube did not enter the Body; but retired with the Tube, otherwise it would have supply’d the Body with the Electricity it had lost. With regard to Powder Magazines My Idea is,

That to prevent the Mischief which might be occasion’d by the Stones of their Walls flying about in case of accidental Explosion, they should be constructed in the Ground; that the Walls should be lin’d with Lead, the Floor Lead, all ¼ Inch thick & the Joints well solder’d; the Cover Copper; with a little Scuttle to enter, the whole in the Form of a Canister for Tea. If the Edges of the Cover scuttle fall into a Copper Channel containing Mercury, not the smallest Particle of Air or Moisture can enter to the Powder, even tho’ the Walls stood in Water, or the whole was under Water.