How, at a window, as far as eye can discover black from white, a man may hold discourse with his correspondent, without noise made or noise taken; being, according to occasion given and means afforded, _ex re natâ_, and no need of provision beforehand; though much better if foreseen, and means prepared for it, and a premeditated course taken by mutual consent of parties. NOTE. The _telegraph_, though not generally used in Europe till the commencement of the French revolution, appears to have been well known to the ancients. Polybius describes a method of communication, which was invented by Cleoxenus, which answered both by day and night. Kircher and Scott likewise allude to its use; but the description given by the Marquis is evidently superior to any that had preceded him; and, indeed, must have nearly resembled that in use at the present period. No. VII. A way to do it by night as well as by day, though as dark as pitch is black. NOTE. The allusion here to a telegraphic communication is likewise sufficiently evident; though it is obvious that, for night signals, it will become necessary to substitute rockets or reflecting lamps for the painted boards. Among the signs for nightly information at a distance, those by fire are extremely common, and have been used by the Chinese, Persians, and other nations, in the remotest times. This species of communication is affirmed by Diodorus Siculus to have been practised by Medea in her conspiracy with Jason, which carries us back three thousand and seventy years; and although there must be some uncertainty on this question, Pliny, in his "History," lib. vii. cap. 56, says, it originated with Sinon. "Specularem significationem Trojano bello Sinon invenit." This was the signal upon which Sinon agreed to unlock the wooden horse in the siege of Troy, about 1184 years before Christ: "----Flammas cum regia puppis Extulerat." _Virgil. Æn._ lib. ii. 256. And, after the taking of Troy, Æschylus relates, that Agamemnon immediately apprized his queen, Clytemnestra, of that event by a similar method; which, we suppose, must have been done either by men placed at certain distances with lighted torches, which they held up in succession, or by a considerable number of fires on the tops of hills, denoting the simple fact previously agreed on between the parties. See Onosander's Strategicus, cap. 25, where this practice is described.