TELEGRAPH. 



TELEGRAPH, ELECTRIC. 



70 



another; Pasley provided against this occurrence with his universal 

 telegraph by the addition of the auxiliary arm, or indicator, marked a, 

 Jig. 8, which, in whatever direction the machine may be viewed, distin- 

 guishes the side at which the numeral signs commence. It serves also to 

 prevent the position marked 4 from being confounded with the stop 

 which it might be if there were nothing to indicate that the telegraph is 

 at work, and to enable the eye to measure its height. The counter- 

 balance weights of the arms are not fixed close to the pivot, but extend 

 to Borne distance from it, in the form of a slender framework of iron, 

 with a ball at the outer extremity, their light appearance rendering 

 them almost invisible at a distance. Pasley states that telegraphs 

 should in general be painted black, and, if possible, so placed that they 

 may be seen without any background. If, however, a background be 

 unavoidable, the telegragh should be of such a colour as to contrast 

 with it. In some cases, where the appearance of the background 

 varies much at different periods of the day, it has been found useful to 

 paint the arms white and black, in large chequers, each occupying 



: the width and half of the length of the arm. 



The contrivances which have been suggested for effecting telegra- 

 phic communication are so very numerous, that anything like an enume- 

 ration of them is impossible in this place. Several depend upon the 

 application of arms of various forma to a semaphoric telegraph, while 

 another class of telegraphic contrivances depend upon the exhibition of 

 devices or symbols, in a manner somewhat resembling the original 

 contrivance of Dr. Hooke. In Mr. Spencer's ' anthropo-telegraph,' a 

 man holds a couple of discs in his hands, and makes signals by placing 

 them in different positions with respect to each other. But the reader, 

 interested in this sort of detail, which i now purely historical, may 

 gratify his curiosity by referring to the ' Transactions of the Society of 

 Macdonald's 'Treatise on Telegraph Communication' (1817), 

 also contains a multitude of similar details. 



Marine telegraphic communication is an object of great importance, 

 since there are many circumstances which render personal communica- 

 tion between vessels at sea impracticable, and that sometimes in cams 

 of the greatest emergency. But, although naval signals have been, of 

 necessity, long used, and flags of various forms and colours have been 

 extensively employed for the purpose of making them, it was not till 

 within a comparatively recent period that they were reduced to 

 nnytliing like an efficient telegraphic system. Sir John Barrow states 

 y. Brit.,' art. ' Navy ') that " The idea of numbering the flags, and 

 of assigning a certain number of corresponding sentences to certain 

 n of these numbers, wag reduced to something approaching 

 a regular system in the fleet of Lord Howe;" and that in the year 

 1798 a new signal-book was issued by the Admiralty, the references to 

 which were made by a numerical arrangement of flags. This book 

 contained about four hundred sentences, expressive of the most usual 

 operations of the fleet ; but it was so imperfect that, if any order had 

 to be transmitted which was not to be found in the dictionary, it 

 became necessary to make the signal for " a boat from each ship ; " an 

 order which could not always be complied with. This inconvenience 

 was remedied by the plan, suggested by Sir Home Popham, of making 

 the flag-signals represent the letters of the alphabet, a* well as words 

 and sentences, in connection with numbers. He also printed, at 

 Calcutta, a new code of naval signals, which was subsequently re- 

 4 in England, greatly extended, and adopted for use in the navy. 

 Among the numerous improvements introduced by him is a new 

 '1 of cutting the signal flags, so that, as he explained to the 

 y of Arts in 1816, " the selvages of the buntin are brought on 

 iter edges of the flags, and the gorings in the centre; by which 

 means the outer edge is susceptible of the least air of wind, and when 

 the flag blows out, the gorings assist in keeping it out ; whereas the 

 old flags had a hem on the outside, which rendered them difficult to 

 be moved without a fresh breeze, especially in damp and rainy weather, 

 as the hem then became very heavy." " Besides," he adds, " it is 

 impossible, from the nature of the buntin, to sew a straight seam, for 

 tin- mutant it u cut it will become in gome degree curved." (' Trans- 

 actions,' vol. xxxiv.) 



The principle of the numerical system as applied to flag-telegraphs 

 in tin- navy is briefly explained by Macdonald. Nine different varie- 

 gated flags are employed to express the numerals 1 to 9, another for 0, 

 md another called a uibtlitute, to repeat any flag under which it is 

 1, in the case of the same numeral occurring twice in the number 

 ti. be expressed. A pendant is also used in some cases as a substitute 

 f<ir the uppermost figure; and thus, by the use of eleven different 

 flags and a pendant, any number from 1 to 999 may be expressed 

 it displaying more than three flags, or two flags and a pendant, 

 at once. 



The Codes belt known in England are those of the Admiralty, 1808, 

 and again in 1816 and 1826, and the modifications which form the 

 it Admiralty Code ; Lynn's Code, 1818 ; Squire's, 1820; Kaper's, 

 Phfllipps'l, 1:(6; Kohde's, 1836; Walker's, 1841; Eardley 

 Wilmofs, 1851 ; Roger's (American), 1854 ; Reynold's (French) 1865 ; 

 Marryatt's (last edit.). IBStJ ; Board of Trade (2nd edit.), 1859. In all 

 these the general principle is the same as above explained. A certain 

 number of flags and pendants of different patterns have to each its 

 own name, some being expressed by numerals, others by letters, while 

 a third set are used for specific purposes : one called the Interrogatory, 

 uks a question ; Another signifies an affirmation, another a negation, 



and so on. In the Admiralty, this system is carried to a considerable 

 extent, and requires about fifty flags or pendants; while there is a 

 general system-book, by which orders are given for evolutions in the 

 fleet, and much routine information. There is also a second telegra- 

 phic book, including common words in English, a list of ships in the 

 Royal Navy, with the names of the flags by which each is distin- 

 guished, and other useful information. There is also a system of 

 night signals, the same as the general signal book, but instead of flags, 

 lamps, with or without blue lights or guns, convey the signals. There 

 is also a system of fog-signals made by the firing of guns, the variations 

 being marked by the intervals between the reports. In addition to all 

 this, each commander is furnished with private and secret signals, 

 which are only used to ascertain whether a ship of war is a foreigner 

 or not ; for if a foreigner the proper return signal will not be known. 



A general code adapted to merchant vessels was invented by Captain 

 Marryatt, and continued in use up to the year 1 357, when the Board 

 of Trade published their ' Commercial Code of Signals for all Nations,' 

 which soon came into general use. It includes only 18 flags or 

 pendants, which were named after the consonants, and were so 

 arranged as to show the distinguishing flag of every British merchant 

 ship, a list of such ships as are registered being published every year 

 by the Board of Trade, with an official number to each. Each ship 

 always retains its name and number, although it may change its port. 

 The signals provided for were 20,000, and 4 flags the greatest number 

 for any signal. The system was modified by a committee appointed 

 by the Board of Trade in 1855, and as now in operation provides by 

 means of 18 flags and 3 pendants for upwards of 70,000 signals : the 

 flags and pendants are given under FLAG. The signals are arranged in 

 classes for easy reference. We may lastly refer to a system of boat- 

 signals arranged by Captain Wilmot. 



Sir John Barrow, in the article before alluded to, observes that a 

 telegraph employed for public purposes should be possessed of power, 

 certainty, rimjilicity, celerity, and tecrecy. It should have sufficient 

 power to express, by distinct positions or combinations of moveable 

 parts, any possible order or information, either by letters, words, or 

 sentences. Its certainty will depend upon all its parts being clearly 

 defined, wholly within the field of the telescope, and so distinct that 

 there shall be no risk of mistaking one signal for another ; whence the 

 importance of simplicity becomes obvious. In order to decide the 

 question as to distinctness, the shutter-telegraph at Nunhead, near 

 New Cross, was left standing for some time on the same hill as the 

 semaphore ; and the result of the trial for a whole winter was, "that 

 the semaphore was frequently distinctly visible when the boarded 

 telegraph was so much enveloped in mist and fog that the particular 

 boards shut or thrown open could not be distinguished ; " and that 

 the number of days in the course of the winter upon which the 

 semaphore was visible exceeded those upon' which the shutters could 

 be seen by fully one-third. 



Any means of telegraphic communication which depends upon the 

 deciphering of signals exhibited at a distant station is necessarily de- 

 pendent upon contingencies of weather; but many plans have been 

 contrived for effecting the object in such a manner as to be inde- 

 pendent both of light and of the state of the atmosphere. For com- 

 munication between the different parts of a house this object may be 

 effected by a mechanical connection, by chains or wires, between two 

 dials with revolving indexes or pointers, in such a way that when one 

 pointer is directed to a particular letter or word inscribed upon the 

 dial to which it is attached, the other may exhibit a similar movement. 

 The attention of the servant is engaged previously by ringing a bell ; 

 and when the required signal has been made, a spring returns both 

 indexes to their original position. Speaking-pipes, or tubes to convey 

 the voice from one place to another, are also available for short dis- 

 tances, but their range is too limited for application on an extended 

 scale. One of the early schemes of this character depends upon the 

 principle of water finding its level ; but, independently of the difficulty 

 which might arise from the friction of water in a very long pipe of 

 small diameter, such as would be required to connect the vertical tubes 

 in which the observations would be made, such a plan involves the 

 necessity of having all the communicating stations at or near the same 

 level. Other hydraulic telegraphs depend upon the comparative incom- 

 pressibility of water or other liquids ; it being proposed to lay down 

 small pipes of any required length, and to indicate different signals 

 by pressing more or less upon the surface of the fluid contained in 

 them, which would transmit the motion to the opposite end of the 

 pipe, where it might be pointed out upon a dial, or in any other con- 

 venient manner. Mr. Vallance described such a method of telegraphic 

 communication in a pamphlet, published in 1825, of which Hebert 

 jives some account (' Engineer's and Mechanic's Encyclopaedia ') ; and 

 some similar schemes have been more recently propounded. Air con- 

 fined in small pipes has also been tried to a limited extent as a pneu- 

 matic telegraph ; but in this, as well as in the hydraulic system, the 

 risk of leakage is a serious disadvantage. 



TELEGRAPH, ELECTRIC. The attempts to render one or other 

 of the phenomena of electricity subservient to the purposes of tele- 

 rraphy, have been numerous. From the earliest date which we can 

 issign to the existence of an electric telegraph, its essential parts have 

 jeen the same. These are, 1st, the source of electrical power; 2nd, 

 ;he conducting material by which this power is enabled to travel to 



