use. 'Tis true, the sphere does not turn so swift, as when the great wheel is used: but swiftness we think of little importance, since a few turns will charge the phial, _&c._ sufficiently. _I am_, &c. B. FRANKLIN. [Illustration] LETTER III. FROM Mr BENJ. FRANKLIN, in _Philadelphia_. TO Mr PETER COLLINSON, F.R.S. _London_. _Farther_ EXPERIMENTS _and_ OBSERVATIONS _in_ ELECTRICITY. _1748._ _SIR_, § 1. There will be the same explosion and shock, if the electrified phial is held in one hand by the hook, and the coating touch'd with the other, as when held by the coating, and touch'd at the hook. 2. To take the charg'd phial safely by the hook, and not at the same time diminish its force, it must first be set down on an electric _per se_. 3. The phial will be electrified as strongly, if held by the hook, and the coating apply'd to the globe or tube; as when held by the coating, and the hook apply'd. 4. But the _direction_ of the electrical fire being different in the charging, will also be different in the explosion. The bottle charged thro' the hook, will be discharged thro' the hook; the bottle charged thro' the coating, will be discharged thro' the coating, and not other ways: for the fire must come out the same way it went in. 5. To prove this; take two bottles that were equally charged thro' the hooks, one in each hand; bring their hooks near each other, and no spark or shock will follow; because each hook is disposed to give fire, and neither to receive it. Set one of the bottles down on glass, take it up by the hook, and apply its coating to the hook of the other; then there will be an explosion and shock, and both bottles will be discharged. 6. Vary the experiment, by charging two phials equally, one thro' the hook, the other thro' the coating: hold that by the coating which was charged thro' the hook; and that by the hook which was charg'd thro' the coating: apply the hook of the first to the coating of the other, and there will be no shock or spark. Set that down on glass which you held by the hook, take it up by the coating, and bring the two hooks together: a spark and shock will follow, and both phials be discharged. In this experiment the bottles are totally discharged, or the equilibrium within them restored. The _abounding_ of fire in one of the hooks (or rather in the internal surface of one bottle) being exactly equal to the _wanting_ of the other: and therefore, as each bottle has in itself the _abounding_ as well as the _wanting_, the wanting and abounding must be equal in each bottle. See §. 8, 9, 10, 11. But if a man holds in his hands two bottles, one fully electrify'd, the other not at all, and brings their hooks together, he has but half a shock, and the bottles will both remain half electrified, the one being half discharged, and the other half charged.