Of the 28 signs. which the Universal Telegraph is capable of exhibiting, I would reject one, namely, position 4 of the day signals, in which one arm points vertically upwards, in the direction of the post proloned ; because it has been urged, that un less when viewed by a very experienced eye, it is liable to be confounded with the post, so as to be mistaken for the position called " the stop," in which neither of the arms is shown.
Of the remaining 27 signs, one should be used as an alphabetical Preparative, one as a Numeral Pre parative, and five as Dictionary Preparatives, each of the latter referring to its own distinct part, or class of the dictionary.
Thus there would be 7 preparatives, and 20 signs for general purposes. Each preparative would of course denote, not only the beginning of that word or sentence which is immediately to follow it, but also the end of the preceding one.
In representing the letters of the alphabet by 20 signs, the letters I and J, the letters K and Q, the letters S and Z, and the letters U and V, would be coupled together ; but the letter would require to be denoted by the two successive letters P H, and the letter X, by the two successive letters, C S or K S.
The number of signals, which may be made by three successive changes on the Telegraph, using the 20 disposable signs only, is equal to 8000, being the third power of 20 ; but as the beginning of each signal must be denoted by a preparative, without which the signal is imperfect, if the above 8000 ar ticles be combined with the five dictionary prepara tives before mentioned, it will be evident, that by never using more than four changes on the Tele graph, for any article of the dictionary, no less than 40,000 words and sentences may thereby be exhibit ed; but, as I remarked before, this number is greater than appears to be absolutely necessary, in a judicious and well composed Telegraphic Dic tionary."
For farther information on the subject of tele graphs, see Polybius, lib. x. cap. 40. Vegetius De Re Militari. Kircher's Jirs Magna Lucis et Umbrte Schottus Technica Curiosa. Marquis of Worces ter's Century of Inventions, No. 6, 7. Kook's Phi losophical Experiments and Observations, by Der ham. Lond. 1726, or Phil. Illag«zine, vol. i. p. 312. Ilook's Phil. Trans. 1684. P. L'Hoste L'Jlrt des armee Novak's. Lyons, 1697. IL L. Edgworth's Irish Transactions, vol. vi. p. 125, and Bibliotheque Brilannique, 1796, vol. i. No. 2. .Journal des Inven tions el decouvertes, 1793, tom. ii. p. 12, 14, and Ni cholson's Journal vol. ii. p. 319. M. Chappe in Hutton's Dictionary, art. Telegraph, and Fourcrov's Report on the System of Telegraphic communication in France will be found in the Moniteur, 1795, No. 109, p. 449, cd. 2. Breguct and Betancourt in the Bulletin de la Societe Philomathique, No. 16, p. 125. M. Macarthur Naval Chronicle, 1797. Rev. J. Gam ble's Observations and Telegraphic Experiments. Colonel Pasley, Phil. Magazine, 1807, vol. xxix. p. 292, Id. 1810, vol. xxv. p. 339, and his Description of the Universal Telegraph. Lond. 1823. Boaz's Nocturnal Telegraph in the Repertory of Arts, 1st series, vol. xvi. p. 233, or l'hil. Mag. vol. xii. p. 84. Edelcrantz On Telegraphs in Nicholson's Jour nal, vol. v. p. 193, and Journal de Physique, vol. lvi. p. 468. Telegraph by the Human Figure in the Memoiressur /es aveugles, and in Nicholson's Journal, vol. vi. p. 164. Much important information on telegraphs, with an account of Colonel Macdonald's own inventions will be found in his Treatise on Tele graphic Communieation, 1808 ; his Expose of the present state of Telegraphic Communication, Lond. 1819, and his General Telegraphic System and Diet.