violently agitated; and the consequence of these agitations we cannot know. It may be said, indeed, that in the operations of nature the electric matter is often violently moved without any sickness taking place; neither in fact did any ensue at the time the powder-mill in question was blown up. But it must be remembered, that, in the ordinary course of nature, if the electric matter is moved, a receptacle is also provided for it. In a thunder-storm, where immense discharges of electricity are made from one cloud, there is another cloud of an electricity opposite to the former ready to receive them, or if not, the earth itself is frequently struck. In eruptions of volcanoes, the smoke receives the electricity discharged, and becomes charged with lightning of a more dangerous kind than that of ordinary thunderstorms; and Sir William Hamilton relates, that in the great eruption of Vesuvius, in 1794, lightning of this kind proceeded from the smoke for no less a space than _seventeen_ days. But in artificial commotions of this fluid, where nature has not provided any receptacle, the phenomena must be quite different; and though we may with safety to ourselves interfere with the operations of fire and electricity to a certain degree, yet we may at last rouse these terrible elements into such action as will prove fatal to great numbers. Hence possibly may arise in part some of those sicknesses which take place after battles, in violent sieges, &c. An instance of this is said to have happened at Valenciennes, when last besieged by the Duke of York. A disease prevailed chiefly among women, children, and persons of a weak constitution; great numbers of whom died so suddenly that it was at first thought to be a plague, until it was found not to be infectious. The blood was found greatly dissolved, and the physicians ascribed it to the monstrous bombardment and cannonading which took place during the siege. Such was the account published in some of the newspapers of the time, and from the subsequent considerations it will not seem improbable that such things may take place.