Telegraph, so named from two Greek words, ῥῶσις, end or distance, and γράφω, I write, is a machine so constructed as to enable two persons to converse with each other at a distance, either by sentences, words, or letters, according to a convention previously agreed upon by the parties. Such a mode of communicating ideas beyond the reach of hearing is not, however, confined to any particular machine; the fingers of the human hand are quite sufficient, as every young boarding-school lady knows, for the purpose; and, when so applied, may be called a telegraph. Thus also the signal-flags used on board ships to communicate with each other, by making them represent letters or numbers, or both, constitute a telegraph; as may also the sending up of sky-rockets, blue lights, the suspension of lanterns, the making of fires on beacon, high hills, &c. be considered as telegraphic communications.
In imitation of the French, however, we have almost indiscriminately adopted the use of the word semaphore for the telegraph, which is perhaps of more extensive application, being derived from σημαία, a sign, and σήμα, I bear; and may consequently be applied universally to whatever means may be used to communicate intelligence by signs or signals. Thus the firing of guns a certain number of times at certain intervals,—the notes of a trumpet, bugle, French horn, or other wind instrument,—the strokes on a drum,—may be used to convey information to a limited extent. The troops and marines which landed on the coast of America in the last war, when scouring the woods in detached parties, were regulated by the notes of the bugle, which were so clearly understood that no false movements were ever made. The immense number of barges and boats which crowd the Imperial Canal of China are directed in their movements, both by night and day, by the sound of the gong. The Indians of America convey intelligence from hill to hill by throwing out their arms with or without staves in them; by spreading their cloaks, holding up skins, &c.; and even the savage Hottentots, called Bosjeismans, the lowest probably in the scale of human beings, communicate with each other by arranging fires on the side of the hills in certain positions.
It is rather surprising that an art so simple as that of conveying ideas by means of signals, so well understood in remote antiquity, and practised even by savages, should have made so little progress in its improvement, that it may be said to have remained in its original rude state nearly down to our own times, when it has almost at once been brought to that state of perfection of which it appears to be capable.
One of the arguments usually adopted to prove that the art of conveying intelligence by signals was known in the early ages of Greece, is deduced from the opening of the Agamemnon of Æschylus, where the man on the watch-tower at the top of the palace announces the fire-signals having communicated the fall of Troy, long before any of the Greeks had returned from the siege; and Clytemnestra afterwards relates the stations; but this event of the burning of Troy, supposed thus to have been known in Greece soon after it happened, proves nothing more than that the use of signals was known to the poet, who wrote eight or nine hundred years after the event. Mention, however, is made by Jeremiah (ch. vi. v. 1), who was at least 200 years before Æschylus, of "setting up a sign of fire in Beth-haccerem;" and such signals are often alluded to by the prophets, as notices of the approach of an enemy.
The earliest decisive proof of telegraphic communications, except these by fires (σημαίαι), being in use among the Greeks, is found in the methods described by Polybius. The Romans had their vexillaria, and used flags and other contrivances for regulating the movements of their armies; and they had hollow tubes constructed in the walls of their cities, by which they could communicate with the several ports or works by sound, as is done in our times in some manufactories by means of pipes or trumpets. Wherever the Romans pitched their camp, an elevated spot was selected for the signal station, to convey intelligence to the foraging parties or detachments; but it is nowhere stated to what extent this was carried. Vegetius alludes to something like a beam in the air, on the same principle perhaps as our semaphore.
In modern times, Kircher, who had more learning and less sense than any man of his day, and has written on almost every subject, gives an idea of telegraphic communication; and so does the ingenious Marquis of Worcester, in his Century of Inventions; but so vague as to convey no notion of the means he was to employ, except the use of colour; for the "discourse" to be held is stated to be "as far as eye can discover black from white." He also throws out a hint for a night telegraph, by which the same may be done, "though as dark as pitch is black." But almost every modern invention is supposed to exist in the mysterious "scantlings" of the Marquis of Worcester.
The first telegraph on record in modern times, applicable to universal purposes, is that of Dr Hooke, described in the Philosophical Transactions of the year 1684. He minutely details the mode in which the stations should be selected, their height and intermediate ground, so that the refraction of the air may not disturb the clear appearance of the object; the telescopes to be used; the characters to represent the alphabet, which, he says, may be varied ten thousand ways, and "none but the two extreme correspondents shall be able to discover the information conveyed;" and so convinced is he of the practical efficiency of his telegraph, as to leave no doubt on his mind, "that the same character may be seen at Paris within a minute after it had been exposed in London." His method consisted in exposing in succession as many different shaped figures, or signs, at least, as the alphabet consists of letters. If used in the day-time, they might be squares, circles, triangles, &c., made of deals; if at night, torches or other lights disposed in a certain order. These characters or signs were to be brought forth from behind a screen on rods, as they might be wanted, and exposed to view. The accompanying figure, where A is the screen, and Monsieur Amantons, of the Royal Academy of Paris, made an experiment to convey intelligence, which was highly approved of by the other members, and several persons of distinction belonging to the court. By the description given of the machine, it seems to have differed very little from that of Hooke already published in the Philosophical Transactions; the signals being either large letters of the alphabet, or figures of various shapes to represent them; the latter being the more valuable, as, by a change of key, the nature of the communication might be kept a secret from those actually employed in making the signals.
It has been supposed that electricity might be the means of conveying intelligence, by passing given numbers of sparks through an insulated wire in given spaces of time. A gentleman of the name of Ronalds has written a small treatise on the subject; and several persons on the Continent and in England have made experiments on Galvanic or Voltaic telegraphs, by passing the stream through wires in metal pipes to the extremities or stations, into phials of water; but there is reason to think that, ingenious as the experiments are, they are not likely ever to become practically useful. Since this was written, Professor Wheatstone has succeeded in contriving a Galvanic telegraph that works admirably, and will no doubt be applied to all the great lines of rail-road in the kingdom. It is simple in its construction, not liable to error, very portable, and carries round the margin of a circle the letters of the whole alphabet in rapid succession, so that each word is speedily conveyed to any distance.
Necessity is said to be the mother of invention; she is also frequently the foster-mother, who calls forth into action, and displays the utility of inventions abandoned by their natural parent. Both Hooke's invention and Amantons' modification were published all over Europe, the former as early as 1684; yet they were not practically applied to any useful purpose till the year 1794, when Citizen Barere, in a report made to the Convention, ascribed the invention then in use to Citizen Chappe.
Chappe's telegraph consists of a beam of wood, moveable on a pivot at the summit of an upright post. At each of the extremities of this beam is a moveable arm, as in the figure. The different positions in which both the beam and its two arms may be placed at angles of $45^\circ$ give to this telegraph considerable powers; but it is too complicated a machine not to be liable to many mistakes, unless worked by long-experienced operators.
In the year 1784, Mr Lovell Edgeworth produced his plan of a numerical telegraph, claiming, at the same time, the merit of having invented a mode of distant communication as far back as 1767, by employing a common windmill, and arranging the various positions of its arms and sails so as to represent a certain number of signals arranged in numerical order.
Mr Edgeworth's telegraph consisted of four wedges or cones, moveable on four upright posts, as under, which, by their different positions, might be used either numerically or alphabetically.
In the year 1795, when the advantages had been made evident which the French derived from M. Chappe's telegraph, the inventive faculties of our countrymen were called into action. Among other proposals, the Rev. J. Gamble produced two plans of a telegraph; the one consisting of five boards, one above the other, which, by opening and shutting singly, or according to all the combinations of which they were capable, gave a certain number of distinct signals, representing either numbers or letters, as might be deemed most expedient. The arrangement of the shutters was as in this figure. The other plan was that of five beams of wood, turning on the summit of a post, so as to form five radii of a semicircle at equal angles of $45^\circ$ with each other, as in the annexed figure.
Among other projects about this time, was that of dividing a large circle into twenty-four parts, to represent the letters of the alphabet, round which a moveable radius was to traverse; then, by placing corresponding divisions, by means of wires, before the object-glass of the telescope, the coincidence of the two radii would mark out the letter meant to be designated. Of this kind, a plan by Mr Garnet approached nearest to efficiency; but, at best, could only be applied to very short distances.
In the same year (1795) Lord George Murray presented his plan of a six-shutter telegraph to the Admiralty, which was the one adopted and made use of during the whole war, and until the year 1816, when it was changed for a simplified semaphore, which will be noticed hereafter. The annexed figure represents that of Lord George Murray.
On the same principle as the radiated telegraph of Mr Gamble, but differently arranged, the French, on the commencement of the second war in 1803, erected signal-posts along the coast, to which they gave the name of semaphores, being two or three beams of wood on the same post, but turning on different pivots.
In 1807, Captain (now Colonel) Pasley published his Polygrammatic Telegraph, which differed only from the French semaphore in having two beams turning on one pivot on the same post, and multiplying the number of posts; which he afterwards (in 1810) changed so far as to place three sets of beams or arms, two in each set, on one post, and thus approaching still nearer to the French semaphore. In the year 1816, Sir Home Popham, who had already introduced a new code of signals into the navy, which was admitted on all hands as a great improvement on the old system, both as regarding the number, the arrangement, and the shape of the flags, now turned his attention to the land semaphore, and proposed one on a construction of the same nature with those of M. Chappe and Colonel Pasley, but much simplified. It was, in fact, nothing more than two moveable arms on separate pivots on the same mast, as in the annexed figure.
This machine, on account of its simplicity, had obviously the advantage over all others that had been proposed; and being found of sufficient power and efficiency for all required purposes, it was adopted by the Admiralty, instead of the shutter-telegraph, which had been in use since the year 1795.
Colonel Pasley, however, in 1822, still further simplified this useful machine, at the expense of sacrificing a small portion of its powers, by making the two arms revolve on the same pivot, as in this figure, to which he has given the name of the "universal telegraph."
The last, but by far the most persevering and voluminous writer on telegraphs, is Lieutenant-Colonel Macdonald, who, in 1808, published what he deems improvements in the system of telegraphic communications, both as they regard the machine itself, and the dictionary to be used with it. He not only gives the preference, but is so much attached, to the shutter machine, that he is quite indignant at its being supplanted by the semaphore; and so far from being satisfied with the powers of which a six-shutter telegraph is capable, he has extended his to no less than thirteen different boards, as in the annexed figure, by which he certainly gains power enough, but not without producing confusion and perplexity.
As the use of telegraphs is chiefly confined to public purposes, and more especially to convey speedy information respecting naval and military armaments and operations, the machine to be adopted, and the system of working it, ought to possess power, certainty, simplicity, celerity, and secrecy. The power of the machine, or the number of distinct combinations of its moveable parts, should be equal to the conveyance of every possible order or information, either by numbers representing the letters of the alphabet, or words, or sentences. To insure certainty, the moveable parts or signs should be so well and clearly defined, so wholly within the field of the telescope, and so completely removed from all ambiguity, as not to be liable to the mistaking of one signal for another; hence the advantage of the simplicity of the machine. And as one of the main uses of the telegraph is to convey instructions or intelligence in a speedier way than the intermediate distance can be travelled over, it is evident that celerity is an important quality of telegraphic communication. It is equally obvious, that if such instructions or intelligence could not be conveyed in secrecy from him who sent it to him who was to receive it, such a system would be highly defective and objectionable.
Bearing these observations in mind, we shall not have much difficulty in determining on the merits of the several telegraphic machines above mentioned. The choice, indeed, appears to lie between the six-shutter telegraph, so long used at the Admiralty, to communicate with the several ports; the semaphore of Sir Home Popham, which superseded it, and is now in use; and the universal telegraph of Colonel Pasley. Colonel Macdonald, who conceives the shutter telegraph as the perfection of the art, boldly asserts that "the semaphore arm of proper dimensions is not to be seen in clear weather so well as the common sized boards, and in cloudy weather by no means so well;" and consequently that, "for this climate, the boarded telegraph is in all respects more advantageous." This would be important if correct; but it is evident that the colonel is not aware of the discussion which took place on this very important part of the subject, on the first adoption of the boarded telegraph. Had he read the clear and decisive observations of Mr Gamble, he would scarcely have ventured upon such an assertion.
"It is a theorem in optics," says Mr Gamble, "that the apparent magnitude of an object varies nearly in the inverse ratio of its distance. Hence it follows, that the larger its dimensions, to the greater distance will it be visible. But the nature of our atmosphere, even in its most transparent state, is such as to render any calculation, grounded on this principle, extremely erroneous; and in general its density so obstructs, and its refracting powers cause such confusion in the rays issuing from those surfaces which are not placed sufficiently distant to be distinct, that their image falling upon the retina is frequently so ill defined, as to render it difficult to determine either their figure or position; for which reasons, that which I shall term insulation is generally a quality more requisite to give distinctness to an object, than magnitude of superficial dimensions."
This is unquestionably true; but Mr Gamble illustrates his position thus: "An example of this distinctness arising from insulation cannot be more readily obtained than by taking a page of printed paper, and fixing the eye on some particular letter (as I); then retiring from it, the letter will be so confused with the surrounding ones, as not to be easily distinguished. But if the same letter (I) be printed on a plain sheet of paper, standing by itself (or insulated), the eye will then not only discern it at a much greater distance, but the image falling single and unencumbered upon the retina, we shall be able to determine whether it be inclined to the right or to the left, or whether it be placed horizontally on the paper."
The shutter telegraph is the printed page, and the arm of the semaphore is the letter (I) on a plain sheet of paper.
But actual experiment has completely proved the fallacy of Colonel Macdonald's assertion, and the justice of Mr Gamble's theory. Every officer serving on the line of telegraphs has stated, that at all times, and more especially in cloudy weather, the arms of the semaphore are seen much better than the boards of the telegraph ever were. Lieutenant Pace, who for many years superintended the Admiralty station, declared, that on the first day after the West Square semaphore was erected, he could clearly distinguish the positions of the arms without a telescope, and accurately take down any signals that could be made, which he had never been able to do, under any circumstance whatever, with the shutter telegraph. He also stated that he had frequently an open communication with the semaphore at West Square, while St Paul's was capt by a fog, which was at all times considered by him and his assistant as the conclusive sign that the boarded telegraph could not be worked. But in order to set the matter entirely at rest, the shutter telegraph on Nunhead, near Newcross, was left standing on the same hill with the new semaphore, in order to try their comparative distinctness, for a whole winter. The result was, that the semaphore was frequently dis- Telegraph. tinctly visible when the boarded telegraph was so much enveloped in mist or fog, that the particular boards, shut or thrown open, could not be distinguished; and it appeared by a journal kept by this officer, that in the course of the winter, the days on which the semaphore was visible exceeded those on which the shutters could be seen by fully one third. If, then, this be the case with a six-bearded telegraph, how much more objectionable must one of twelve shutters be, which must necessarily be placed so near to each other as to make it at all times a matter of difficulty to discern at once how many, and which of them, are closed, and which open? Even in the six-shutter telegraph, one board has frequently been mistaken for the other; for it may be remarked, that such a mass of timber as is required for a shutter-telegraph is seldom free from haze.
It will probably be urged, that the arms of the semaphore, having to describe a larger circle, must be slower in their operations; but this increased slowness is so amply compensated by the ease and certainty of reading off the signals as to render any such objection of little or no weight; it may make the difference of one second in each signal, while the machinery by which the semaphore is worked is as simple and as little liable to be out of order as that of the boarded telegraph.
The six-shutter telegraph, it is true, has greater powers than the two-armed semaphore, and much greater than the universal semaphore of Colonel Pasley; that is to say, the number of combinations which it is capable of making without using the stop-signal (or signal which separates one word or one sentence from another), is much greater than in either of the other two; but all of them have sufficient powers, and a sufficient number of combinations, to convey with facility and despatch any communication whatsoever, and in any language, either by letters, words, or sentences. Their respective powers may be seen by the following tables of their positions.
**Admiralty Six-shutter Telegraph.**
| No. of Signal | Signification | No. of Signal | Signification | No. of Signal | Signification | |--------------|---------------|--------------|---------------|--------------|---------------| | 1 | A | 9 | 1235 | | | | 2 | Z | 6 | 1236 | | | | 3 | X | 5 | 1245 | | | | 4 | W | 4 | 1246 | | | | 5 | B | 0 | 1255 | | | | 6 | F | 1 | 1345 | | | | 12 | L | 2 | 1346 | | | | 13 | O | 6 | 1356 | | | | 14 | V | 3 | 1456 | | | | 15 | U | 8 | 2345 | | | | 16 | H | G | 2346 | | | | 23 | Qu | C | 2356 | | | | 24 | R | D | 2456 | | | | 25 | T | E | 3456 | | | | 26 | S | Y | 12345 | | | | 34 | P | 12346 | | | | | 35 | N | 12356 | | | | | 36 | I | 12456 | | | | | 45 | O | 13456 | | | | | 46 | K | 23456 | | | | | 56 | M | 1234 | 123456 | | |
In all, sixty-two separate and distinct signals, which may be made consecutively in any order, without requiring any stop-signal when applied to spelling. The letters of the alphabet opposite to the signals, and the numbers from 1 to 6, may be changed in every possible way.
When spelling is intended to be used, the number of changes need not, of course, exceed that of the alphabet; the rest, as in the table, may be applied to numbers; and what still remains may be made to represent words that are most commonly in use; as, for instance, admiral, captain, ship of the line, frigate, arrived, sailed, harbour, &c., in the navy; or, if military, general, regiment, camp, &c.
**Admiralty Semaphore now in use.**
| No. of Signal | Signification | No. of Signal | Signification | No. of Signal | Signification | |--------------|---------------|--------------|---------------|--------------|---------------| | 1 | 1 | 15 | G | 43 | X | | 2 | 2 | 16 | H | 44 | Y | | 3 | 3 | 21 | I | 45 | Z | | 4 | 4 | 22 | K | 46 | | | 5 | 5 | 23 | L | 51 | | | 6 | 6 | 24 | M | 52 | | | 1 | A | 25 | N | 53 | | | 2 | B | 26 | O | 54 | | | 3 | C | 31 | P | 55 | | | 4 | D | 32 | Qu | 56 | | | 5 | E | 33 | R | 61 | | | 6 | F | 34 | S | 62 | | | 11 | 7 | 35 | T | 63 | | | 12 | 8 | 36 | U | 64 | | | 13 | 9 | 41 | V | 65 | | | 14 | 0 | 42 | W | 66 | |
In all, forty-eight separate and distinct signals, being the whole which the two arms are capable of making, as in the annexed figure; in which the two arms actually exhibited (in black lines) represent the number 16 or H, according to the table or key, as above arranged.
We have here, in addition to the alphabet and the numeral digits, thirteen signs over, applicable to the names of stations, preparative, finish, stop-signals, &c.
**Colonel Pasley's Universal Telegraph.**
| No. of Signals | Signification | No. of Signals | Signification | No. of Signals | Signification | |----------------|---------------|----------------|---------------|----------------|---------------| | 1 | A | 15 | L | 36 | V | | 2 | B | 16 | M | 37 | W | | 3 | C | 17 | N | 45 | X | | 4 | D | 23 | O | 46 | Y | | 5 | E | 24 | P | 47 | Z | | 6 | F | 25 | Qu | 56 | | | 7 | G | 26 | R | 57 | | | 12 | H | 27 | S | 67 | | | 13 | I | 34 | T | | | | 14 | K | 35 | U | | |
In all, twenty-eight separate and distinct signals; containing a sufficient number for expressing the letters of the alphabet, and, consequently, for spelling any message; but not a sufficient number left to express the numeral digits by single signs. The signal No. 4 is, besides, as Colonel Pasley is aware, liable to be mistaken, it being a mere elongation of the mast, which, at a great distance, and owing to the refractive power of the atmosphere, will always be ambiguous when exhibited as a single signal. But Colonel Pasley has added a short arm, which he calls an indicator, as below at A; and which, when made moveable, more than compensates for this defect.
It was with a different view, however, that he has added this indicator. It was suggested to him by a captain in the navy, who had experienced the greatest inconvenience, in using Sir Home Popham's ship-semaphores, from the signal-men confounding the positions of the arms when seen in reverse. We apprehend no experienced signal-men could possibly make any mistake in merely changing the right hand for the left.
The respective powers of the three telegraphs, in making single, or what may be called primary signals, are, as appears from the tables, 62, 42, and 28. In making two changes, with a stop between them (that is, three signals), to represent a word or sentence, their powers will be as 3844, 1764, and 784; in making three changes (or, with the stop, four signals), as 238,328-74,088-21,952. Now, as the telegraphic dictionary of Sir Home Popham, which has been, and still is, used in the navy, does not exceed 13,000 words and sentences, and has never been found deficient in any of its divisions of subjects, it is evident that even the lowest power of the three is more than sufficient for all useful purposes; and that those compilers who have swelled out their telegraphic dictionaries to upwards of 100,000 (one mentioned by Colonel Pasley has extended his labours to 140,000), have made them nearly useless, by the difficulty and loss of time in finding the required phrase or sentence. We have actually seen in one telegraphic dictionary 126 pages, of three columns in each page, and sixty sentences in each column, containing upwards of 20,000 sentences (about one third of the number of words in Johnson's Dictionary), and each of these sentences beginning with the personal pronoun HE, twenty pages with IF, &c. Compared with the use of such a dictionary, spelling the sentences is infinitely preferable as to certainty, and in many cases as to celerity. Indeed we should say that the abbreviated nature of communications made by telegraph renders spelling by far the most eligible mode. In clear weather, the rapidity of working single signals, the short compass within which any message may be condensed, the impossibility of committing any mistake that cannot be immediately rectified, more than compensates for the difference of a few minutes which the use of sentences may probably save. In cloudy or foggy weather, the latter method will always be liable to mistake. If experience may be assumed as a guide, the practice at the Admiralty, of spelling all sentences, for the last thirty years, must decide in favour of that system.
In making use of the alphabetical table, much time may be saved by condensing the message into the briefest form possible, leaving out of the sentences such words as may not alter the sense, and generally the vowels of words. For instance, "Order the Agamemnon out of harbour, and direct her to proceed to Spithead." To convey this message alphabetically, it would be quite enough to say, "Agmenn to Spthed." If "from Spithead into harbour," "Agmenn nto hrbr." In spelling, too, it is very desirable, especially in our foggy climate, that the intelligence to be conveyed should be compressed as much as possible into the early part of the message. By not observing this rule, a curious mistake is said to have been made in the course of the Peninsular war. The admiral at Plymouth endeavoured to send up a message, but a fog coming on, part of it only on that day reached London. It began thus: "Wellington defeated"—and the rest was stopped by the fog; the anxiety for the remainder may readily be conceived; it came, however, complete towards the evening, and conveyed the intelligence, that "Wellington defeated the French," &c. Had the message been thus framed, "French defeated at," &c. (the word Wellington being quite superfluous), the anxiety for the particulars would have been of a very different kind. Much therefore depends, as far as celerity and certainty is concerned, on the construction of the sentence containing the intelligence to be conveyed.
The methods suggested for making use of telegraphic communications by night have not been less numerous than those for the day, though on land there are very few occasions on which they can be of the least possible use. A regiment might perhaps be ordered to move, at a moment's notice, in order to reach a particular point at a given time; or, as an extreme case, the enemy's fleet might be seen towards the close of the day in a particular quarter, which would make it desirable to have the intelligence conveyed in various directions; but no naval movement could take place during the night at any of the ports. So little useful, indeed, does a night telegraph for the navy appear to have been considered, that, with all the facility of applying lamps to the shutter-telegraph at the Admiralty, no attempt was ever made for carrying such a purpose into execution. Colonel Pasley's description of the application of his Universal Telegraph to night-signals will suffice to show one method (as good as any other, perhaps) of adapting the machine to this purpose.
"For night-signals, one lantern, called the centre-light, is fixed to the top of the post; and one lantern (I), as an indicator, is fixed to a light crane or derrick attached to the post, by night only, as under.
"These lanterns are stationary, and appear on the same level. Two other lanterns are suspended to the ends of the arms, upon fixing which a couple of weights are added to counterpoise them. Each of the two arms by day, and each of the two moveable lights by night, is capable of exhibiting the seven positions, besides position O pointing vertically downwards. The indicator serves to distinguish the low numbers 1, 2, 3, from the high numbers 7, 6, 5, in whatever direction the telegraph may be viewed."
The use of telegraphic communication, important as it may be on land, is far more so in the management of a fleet at sea. On the unfortunate result of Admiral Keppel's engagement, Dr Beatson, in his Memoirs, thus expresses himself: "The defects or impropriety of the signals having thus appeared clearly to be the true and sole cause of the miscarriage which disappointed the reasonable hopes of Britain on this critical and weighty occasion, we may be justified in observing, that if an admiral cannot command all the necessary movements of his ships by signal on the day of battle, he is not upon a footing with an enemy who possesses that advantage; and even with better ships and better men, and more experienced commanders, he may be foiled in his expectations of victory, if not defeated, from his want of the means to direct and to perform the necessary evolutions of his fleet."
In the Fighting and Sailing Instructions of the Duke of York (afterwards James II.), a certain number of signals are established for certain movements and manoeuvres of the fleet, each flag having its respective object. L'Art des Armées Navales de le P. l'Hoste, published at Lyon in 1697, contains something like a system of signals, but so awkward and clumsy as to be of a very limited use. Indeed the best signals made use of, down to the American war, could only Telescope be considered as expedients; the numerical plan having never once been attempted, though Dr Hooke, De la Bourdonnois, and some others, had long before suggested it.
In 1798 a new signal-book was issued by the Admiralty, containing about four hundred sentences, for which flags were appropriated numerically, expressive of certain operations of a fleet, which were sufficiently useful as far as these sentences went; but when it became necessary to issue any order not to be found among them, the communication was obliged to be made by boats, and "a boat from each ship" was ordered. The state of the weather did not always render this practicable; and when it was, men's lives were frequently exposed to imminent risk. To remedy this inconvenience, Sir Home Popham printed at Calcutta a numerical code of naval signals, which was reprinted in England in 1803. He afterwards extended the code very considerably, which, by a recommendation of a committee of naval officers, has been adopted, and is now in general use in the navy. The only objection to this code, which more or less applies to all that have subsequently been proposed, is the great number of flags, &c., required for making numerical signals to the extent as laid down in the code in question; and which consists of nine flags, five cornettes, five triangles, and five pendants. With such a number it is next to impossible to make out, in calm weather, the figure and the colour of the flags; and equally so when in situations where, though expanded by the wind, they present only an edge to the eye of the observer, when the distance is not too great, so as to sink the hull of the ship behind the curvature of the earth. The semaphore or sea-telegraph of Sir Home Popham comes in aid of, and indeed entirely removes, those difficulties. It consists of two posts, with a moveable arm to each (see the article Navy), and may be removed to any part of the deck; but we are not sure, simple as it is, that the Universal Telegraph of Colonel Pasley, consisting of one post and two arms, might not be adopted with advantage as a sea-telegraph. The former exhibits eight, the latter seven positions.