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. It has been already proved, that when the globe is put in _motion_, and your hand is applied to it, it _grinds_ to pieces the air between the globe and the hand, and so _rarefies_ and _expands_ it, and sends it off with great force, in the same manner, as _light_ is sent from any body of _fire in action_; as may be seen, if the electrical machine is set at work in the dark; when the emission from the glass globe will appear lucid. The wires which are hung over the glass globe, by the _smallness_ of their _pores_, admitting nothing through them but _light_, and light being a body so _subtil_, as to penetrate the _pores_ of all other bodies, even to the very center of the earth; the _interstices_ of the _wires_ are filled with it from one end to the other. As the _light_ is one continued body, throughout the whole extent of the wire, the _force_ it receives at the end next the glass globe, is _immediately_, and at the _same instant_ of time, communicated to the other end, let the _length_ or _extent_ of the wire be ever so great. As, for example, a pipe of any length, being filled with any sort of fluid, as water; if you force in more water at one end, the same moment, and in the same quantity, it will be forced out at the other. By these experiments in electricity, we find that _fire_ and _light_ are produced as has been before observed, only by _breaking_ the air to pieces, and putting it in _motion_; and that _fire_ and _light_ are in _all_ bodies, water and ice not excepted; for, if a piece of ice is hung at the end of the wire, it will set fire to spirit of wine, as well as an egg.