NMSAT :: Networked Music & SoundArt Timeline

ca - 150 BC __ Pyrsia — Alphabetical fire system
Polybius (ca 204-122 BC)
Comment : Another system invented by Cleoxenus and Democlitus, and perfected by Polybius (- 204 - 122 BC) himself, spells out the words completely, but in its working, as he acknowledges, requires attention, and more than ordinarily close observation. Polybius, a Greek stateman and historian, describes (lib. X, cap. 45, “General History” or “Histories”) his optical telegraph, “Pyrsia”, because the signals were invariably produced by means of firelights.an unquestionable improvement upon the modes of communication which had been previously suggested by Cleoxenes and Democritus. It consisted of a board upon which the twenty-four letters of the Greek alphabet were arranged in five columns, one space being vacant. The party signalling would hold up with his left hand a number of torches indicating the column from which the desired letter was to be taken, while in the right hand he would hold up to view as many torches as were necessary to designate the particular letter required. (Paul Fleury Mottelay. It is this. Divide the alphabet into groups of five letters, in regular sequence, and write each group in order down a board of suitable height. There will be five boards, the last bearing only four letters, which will be no hindranc)hence, raise two torches on the left, five on the right ; P, fourth tablet, second place,.raise four torches on the left, two on the right ; and so on. The boards are set up near the stenoscope, and a fence constructed to the right and left, for ten feet each side, as high as a man's head, at the ends of which the torches shall be raised in order that the receiver may clearly distinguish the right position from the left, and the torches may be hidden when lowered behind the fence. Polybius closes this discussion with a characteristic remark:.« I was led to say this much in connection with my former assertion, that all the arts had made such progress in our age that most of them were reduced in a manner to exact sciences ; and therefore this too is a point in which history properly written is of the highest utility. » It may be remarked, that the systems here described presume the use of torches, not beacon-fires, because the light must be extinguished instantly, or be easily put out of sight. Hence the distances between stations must be comparatively short; ten miles is now found to be a range of convenient limit. Yet the language of Poly bins is based entirely upon the notion of one telegrapher and one receiver only. These, therefore, must be taken as types merely, if he contemplates the transmission of messages, as he says is possible, over a distance of three or four days' journey, or even more. That either of the systems mentioned was ever practically employed in antiquity, I find no evidence ; but that of Polybius contains the fundamental principle of the best modern system of signalling. What Polybius means by a journey of three days may be seen (II. 55) from his giving this as the distance from iEgium to Megalopolis, which is sixty-five to seventy miles as measured on the map, and through one of the regions of Greece most toilsome to traverse. (Augustus Merriam)Further improvement was suggested in the first hal of the third century AD by Sextus Julius Africanus (232 - 290 AD) an eminent Christian historical writer. [...] The many mountain peaks and the clear atmosphere afforded ideal conditions for the operation of beacon fires and beacon smoke signals. (R.W. Burns)
French comment : Cléomène, Damocrite, et ensuite Polyben voulurent donner plus de simplicité à [la méthode des signaux à l’aide de feux assignés aux lettres de l’alphabet, décrite par Jules l’Africain]. Polybe nous apprend qu’il divisoit l’alphabet en cinq colonnes dont quatre de cinq lettres chacune, et une de quatre ; il cachoit des torches derrière deux murailles, placées l’une à sa droite, et l’autre à sa gauche ; et, pour indiquer à son correspondant la vingt-quatrième lettre, il faisoit apparoître d’abord cinq torches à sa droite, qui indiquoient le cinquième division de son alphabet ; puis autre torches à sa gauche, pour marquer le rang que la lettre avoit dans sa division. On fixoit un long tuyau à chaque muraille, qui servoit à diriger la vue vers le point qu’on vouloit observer. Cette méthode ne produit que de foibles résultats. Rollon pense qu’lle ne pouvoit servir qu’à une petite distance, et nous croyons qu’elle n’est utile dans aucune circonstance, à moins que ce ne soit d’une station à uen autre ; car en supposant, ce que nous sommes loin d’admettre, qu’on pût faire passer ces signaux par un grand nombre de stations, sans confusion, et sans avoit besoin de corriger des erreurs, elle nécessiteroit, pour un mot, un si grand nombre de signaux, qu’une nuit employée toute entière suffiroit à peine à une transmission de quelques mots. Chaque lettre employeroit cinq à six signaux, en supposant un terme moyen, et par conséquent de vingt-cinq à trente pour un mot de cinq à six lettres. On perd de vue le système alphabétique depuis Polybe jusqu’au seizième siècle. (Ignace U.J. Chappe, pp. 26-27)
Original excerpt : « The most recent method, devised by Cleoxenus and Democleitus and perfected by myself, is quite definite and capable of dispatching with accuracy every kind of urgent message, but in practice it requires care and exact attention. It is as follows: We take the alphabet and divide it into five parts, each consisting of five letters. There is one letter less in the last division, but it makes no practical difference. Each of the two parties who are about to signal to each other must now get ready five tablets and write one division of the alphabet on each tablet, and then come to an agreement that the man who is going to signal is in the first place to raise two torches and wait until the other replies by doing the same. This is for the purpose of conveying to each other that they are both at attention. These torches having been lowered, the dispatcher of the message will now raise the first set of torches on the left side indicating which tablet is to be consulted, i.e., one torch if it is the first, two if it is the second, and so on. Next he will raise the second set on the right on the same principle to indicate what letter of the tablet the receiver should write down. [...] Upon their separating after coming to this understanding each of them must first have on the spot a “viewing tube. » (with two cylinders, so that with the one he can observe the space on the right of the man who is going to signal back and with the other that on the left. The tablets must be set straight up in order next the tubes, and there must be a screen before both )
Source : Merriam, Augustus C. (1890), “Telegraphing Among the Ancients”, Papers of the Archaeological Institute of America, Classical Series III, Vol. 3, n°1, Cambridge : University Press, printed by John Wilson and Son, p. 12-14.
Source : Burns, R.W. (2003), "Communications : An international history of the formative years", Chapter 1 / Communication among the ancients, IEEE History of Technology Series 32, pp. 12-16.
Source : Fleury Mottelay, Paul (1922), “Bibliographical History of Electricity and Magnetism, Chronologically Arranged”, Read Books (2008), p. 19.
Source : Chappe, Ignace Urbain J. (1824), "Histoire de la Télégraphie", Paris : chez l'auteur.

No comment for this page

Leave a comment

:
: