11. When a bottle is charged in the common way, its _inside_ and _outside_ surfaces stand ready, the one to give fire by the hook, the other to receive it by the coating; the one is full, and ready to throw out, the other empty and extremely hungry; yet as the first will not _give out_, unless the other can at the same instant _receive in_; so neither will the latter receive in, unless the first can at the same instant give out. When both can be done at once, 'tis done with inconceivable quickness and violence. 12. So a strait spring (tho' the comparison does not agree in every particular) when forcibly bent, must, to restore itself, contract that side which in the bending was extended, and extend that which was contracted; if either of these two operations be hindered, the other cannot be done. But the spring is not said to be _charg'd_ with elasticity when bent, and discharg'd when unbent; its quantity of elasticity is always the same. 13. Glass, in like manner, has, within its substance, always the same quantity of electrical fire, and that a very great quantity in proportion to the mass of glass, as shall be shewn hereafter. 14. This quantity, proportioned to the glass, it strongly and obstinately retains, and will have neither more nor less, though it will suffer a change to be made in its parts and situation; _i. e._ we may take away part of it from one of the sides, provided we throw an equal quantity into the other. 15. Yet when the situation of the electrical fire is thus altered in the glass; when some has been taken from one side, and some added to the other, it will not be at rest or in its natural state, till 'tis restored to its original equality.--And this restitution cannot be made through the substance of the glass, but must be done by a non-electric communication formed without, from surface to surface. 16. Thus, the whole force of the bottle, and power of giving a shock, is in the GLASS ITSELF; the non-electrics in contact with the two surfaces, serving only to _give_ and _receive_ to and from the several parts of the glass; that is, to give on one side, and take away from the other.