In such a vertical section of a tooth three distinct substances are seen; namely, the dentine or ivory (Fig. 1, aa. which forms the greater mass, and, as it were, the mould of the tooth, and which contains the pulp cavity (b); the enamel (cc), by which the crown or exposed part of the tooth is covered; and the bone, cement, or crusta petros (dd), which forms a thin layer around the fang, except : that part at which the vessels enter the pulp, and is costinued in a finer and scarcely perceptible layer over the enamel. TEETH. Since the article DENTITION was written, the | them, and polishing them on a hard and smooth whetteeth have been subjected to the most careful microscopic stone. For general examination, lenses magnifying about examination, and the result has been the acquisition of a 50 diameters are sufficient. great amount of knowledge in regard to both their structure and their mode of growth. Indeed there is probably no part of physiology in which more remarkable and important progress has been made during the last ten years than in this, to which the name of Odontography has been given. The chief discoveries were made coincidentally by Professor Purkinje of Breslau and Professor Retzius of Stockholm. The former published his observations in 1835, in the inaugural dissertation of Dr. Fraenkel (De penitiori Dentium Structura), and in that of Dr. Raschkow (Meletemata circa Dentium Evolutionem); and the latter communicated his descriptions to the Royal Academy of Sciences at Stockholm, in whose Transactions they were published in 1836. In 1839 Dr. Schwann published, in his Mikroskopische Untersuchungen,' an account of the modes in which the several constituent tissues of the teeth are developed; and in the same year Mr. Goodsir (Edinburgh Medical and Surgical Journal, vol. li.), carrying out the view before suggested by Professor Arnold, described that method of their early growth which is now generally received as the truth. Mr. Owen also, in his Odontography,' and in various papers, at the same time that he has confirmed and greatly added to the facts described by those already mentioned, has proved, by his investigations into their comparative anatomy, that the minute structure of the teeth may be taken as one of the most certain characters for the discrimination of the genera, and even of the species, of both existing and extinct animals; and he has already applied his knowledge of them to the determination of some of the most difficult questions of palæontology. In the following account scarcely any of the discoveries will be detailed except such as relate to the structure and physiology of the human teeth; for, various as the structures are in the different classes of animals, yet there is so much analogy among them, that the description of the tooth of one will, in great measure, explain the general plan of structure in the rest. Besides, the lately published articles on comparative anatomy contain nearly all the important facts regarding the structure of the teeth in the animals of which they treat. The bone, or cement, has in each animal a minute strueture similar to that of which the bones of its skeleton arr composed. In man it consists of a basis of homogeneos substance, a compound of cartilage and earthy matter..: which there are minute cavities (Fig. 2), with delicat: branched canals leading from one to the other. On the walls of these canals and cells the earthy matter is deposited more thickly than in the intermediate spaces, so that when examined by transmitted light they appear black or dark grey. The cavities, or bone-corpuscles, in man are roun: or oval, and flattened; most of them are between and of an inch in length, about one-third as much in breadt and one-sixth as much in thickness. They have somewhat jagged edges, from all parts of which there proceed the fine branching canals, to which the name of calcige rous has been given, and which traverse the homogeneo basis of the bone, and communicate irregularly with co another. The diameter of these canals, at their largest parts, is not more than 1 of an inch; that of ther smaller branches is between and Their genera direction is towards the axis of the tooth, around which the corpuscles are arranged in concentric circles. Fig. 2. Microscopic view of bone-corpuscles and calcigerous canals. The best method of preparing teeth for microscopic examination is to immerse them in dilute hydrochloric acid, till their earthy matter is so far dissolved that thin transparent slices may be cut from them with a knife; or, without softening them in acid, to make thin sections, in thea, about of an inch thick, set side by side and upvertical and other directions, with a fine saw, and to reduce these to the necessary thinness and transparency by filing Fig. 1. right upon the ivory of the crown of the tooth (b. One rough outer surface of the ivory; the other, which is end of each prism is fixed in a little depression on th somewhat larger, is turned towards the masticating surface of the tooth in the direction in which the chief external pressure is to be resisted. The course of the pri-ms is more or less wavy, their curves being, for the most part, parallel (Fig. 4), but sometimes opposed. Most of the extend from the ivory to the surface of the tooth; an. where they do not, small complemental prisms fill up like wedges, the vacant spaces. a Fig. 4. Small collection of enamel-fibres. Manifei section of a bicuspid tooth. View of the arrangement of the enamel-fibres In the perfect state the enamel contains so small a quantity of animal matter, that it cannot be demonstrated to the sight, and the prisms are inseparably consolidated; but in young teeth it is soit, and may be broken up arte its elementary parts. In the early state also it exhibits pertions of a membranous animal substance, consisting of the cells in which each of its prisms was formed; for, as will be presently shown, the earthy matter is deposited in what might be called a set of moulds formed by the primary cells of the enamel membrane, and, as it accumulates, the membrane of the cell is so nearly removed, that in the perfect tooth no portion of it can be discerned. Its former existence however seems to be indicated by fine close-set transverse striæ upon each prism of the enamel. The dentine, or ivory, is composed of a hard fibrous basis of cartilage and earthy substance, traversed by very fine, branching, cylindrical tubules, which run in an undulating course from the pulp-cavity, on whose internal surface they open (see Fig. 1, b) towards the adjacent part of the exterior of the tooth. Each tubule in its course outward makes two or three chief curves (primary curvatures,' Owen), and is besides bent at every part in minute and very close undulations, or secondary curvatures; but the course of those tubules, which are adjacent to each other, is very nearly parallel. It is from the parallelism of these secondary curvatures of the tubules, that the appearance arises, as if the ivory were composed of concentric lamella arranged round the pulp-cavity. The chief branchings of the tubules of the dentine are dichotomous (Fig. 5); but they also frequently give off minute branches, which again sending off smaller ones, fill up the spaces between the trunks (Fig. 6). At the trunk each tubule has an average diameter of about rods of an inch, and the distance between each two tubules is nearly equal to the width of three of them. Both the walls and the cavities of the tubules, as well as the substance between them, are filled by the earthy constituent of the ivory, which is deposited in fine granules. The basis of the intertubular substance seems to be composed of bundles of flat, pale, granular fibres, whose course is parallel to that of the tubules. Fig. 6. Fig. 5. Views of the tubules of dentines. A separate organ is provided for the formation of each of these three constituent parts of the tooth, though, when they are perfected, they contain no vascular tissue but the pulp within the pulp-cavity, and it is doubtful whether, in the human subject, fresh material is ever formed from this after the tooth has once attained its complete development. The first appearance of the pulp of each tooth is in the form of a minute process or papilla rising from the bottom of a groove in the mucous membrane of the mouth behind the edge of the jaw. In course of time, as the borders of the groove grow around it, the papilla seems to sink into the mucous membrane; and it now appears as if rising from the base of a follicle, or of a flask-like depression, in the edge of the jaw. And lastly, processes of membrane, or opercula, grow from the sides of the mouth of the follicle, and as they approach each other and adhere by their mutually opposed edges, they gradually close it, and convert it into a capsule or sac, to the base of which the first-formed papilla is affixed. In the first-appearing tooth, the papillary state may be seen in the human embryo an inch in length: the capsular stage is completed at about the fifteenth week of embrycnic life. These three stages of the formative organs of the tooth, namely, the papillary, the follicular, and the capsular, being completed, the substances of the tooth itself begin to be produced. The dentine is developed from the papilla, which gradually assumes the form and relations of the proper tooth-pulp; the enamel, from a special organ developed at that part of the capsule which is opposite to the papilla; and the bone probably from the interior of the capsule itself. The papilla and the sac both gradually increase in size, but the growth of the latter is at first more rapid than that of the former, and the space between them is thus enlarged. Within this space there is deposited from the wall of the sac a soft, granular, non-vascular substance, the enamel-organ, or, as Mr. Hunter (Natural History of the Teeth) termed it, the external pulp. And at the same time as this is being produced from the interior of the sac, there is formed on the surface of the papilla a peculiar structureless membrane, which has been called the preformative membrane, and which, when the papilla begins to ossify, presents numerous little elevations and depressions, on which the enamel fibres are afterwards fixed; for as the papilla enlarges, the preformative membrane comes in contact with the enamel-organ, and they are exactly moulded the one upon the other. Both the papilla, or as it may now be called, the pulp, and the enamel, are composed of primary cells [NUTRITION], and it is by the transformation of these that the tubules of the dentine and the fibres or prisms of the enamel are severally produced. The exact mode however in which the change is effected is not yet known. All that can be seen is that the superficial cells of the pulp, which are at first round or oval, and nucleated, assume the same diameter and direction as the trunks of the dentine tubules, and then have earthy matter deposited in and around them. And these changes go on gradually from without inwards: as fast as the elongated and branching cells of one layer are ossified, those of the layer beneath them become elongated in preparation for the same change; and so on, till a great part of the pulp is hardened. It is due to this gradual ossification of the pulp from without inwards, that in growing animals, to whom madder is alternately given and omitted in their food, the dentine is found to consist of alternate rings of red and white ivory; for while madder is being taken, all the earthy matter that is deposited in the most superficial layer of the unossified pulp-cells is dyed by its colouring principle, and when it is discontinued the same material is deposited uncoloured in the layer of cells which is subjacent to that already Iossified and reddened. When nearly the whole of that part of the pulp which was formed in the original papilla is thus hardened by the deposition of earthy matter, its base begins to grow into one or more conical processes, and, by a hardening of these, through a process like that just described, the fangs are formed, and the tooth rises to the surface of the gum. In the formation of the enamel, the primary nucleated cells on the inner surface of the enamel-organ become elongated and cylindrical, or prismatic; they assume a direction which is perpendicular to the surface of the hardening pulp; and then, their nuclei disappearing, they also are hardened by the deposition of earthy matter within them, which is continued till they are inseparably compacted, and their original membranous wall is not discernible. These changes also, like the preceding, make progress in layers; but the progress is here from within outwards, and it goes on till nothing is left but a thin external enamel-membrane on the surface of the crown oʻ the tooth. As the enamel organ and the papilla, both growing and hardening, approach more nearly to each other, the preformative membrane also disappears. By the transformation of this enamel-membrane, or of the superficial part of the capsule itself, that part of the bone is produced which envelopes the enamel; and by similar changes in that part of the capsule. which has grown in company with the fang-processes of the pulp, that part of the bone is formed which invests the fangs. The changes in this part of the process are probably exactly similar to those through which new bone is produced between a periosteum and the old bone which it sur rounds. TEETH OF WHEELS. [WHEELS.] TEFZA. MAROCCO.] TEGERNSEE, THE, is a lake in the circle of the Isar in the kingdom of Bavaria, about thirty miles from Munich, | at the foot of the Bavarian Alps. It is about four miles long, one mile and a quarter broad, and 300 feet deep. This lake gave its name to a Benedictine abbey, which was founded by the Agilolfingers, in the time of King Pepin, was destroyed by the Hungarians, restored in 979, and not abolished till some years after the beginning of this century. The abbots were princes, and had four hereditary offices in their household which were held by noblemen. The late king of Bavaria, Maximilian Joseph, had the abbey converted into a fine palace, which he presented to his consort the late Queen Caroline, with the lordship depending on it, which is about 60 square miles in extent, including the village of Tegernsee, with 300 inhabitants. This palace is situated in a beautiful country surrounded with lofty mountains, among which the Waldberg and the Setzberg are sometimes illuminated when there are royal visitors at the palace. The grounds are laid out with great taste, and the village church is very handsome, and contains some fine paintings. In the vicinity there are quarries of fine marble of various colours, and the mineral springs of Kreuth and Schwaighof. Kreuth is in a very romantic situation, at the foot of high mountains, and is much frequented for its sulphureous waters. Near Tegernsee naphtha is found, which is here called St. Quirinus oil, because it was formerly pretended that it issued from the corpse of St. Quirinus, to whom a chapel in the vicinity is dedicated. (Hassel, Geographie; Stein, Geographisches Lexicon; Cannabich, Lehrbuch der Geographie; Hübner, ZeitungsLexicon.) TEHERAN, or TEHRAN. [PERSIA.] it to the earl of Mornington, and was created an Insl. p. by the title of Baron Teignmouth. 6 Upon the death of Sir William Jones, in April, 174, Sir John Shore was elected president of the Asiatic Sciety; and taking his seat in that capacity on the 22nd May, he delivered a discourse on the merits of the la president, which is printed in the fourth volume of the Society's Transactions. After his return home L Teignmouth published, in 1804, a 4to. volume, entitle Memoirs of the Life, Writings, and Correspondence of William Jones; and in 1807 he produced an edition, 13 vols. 8vo., of Jones's Works, with this Life prefixed Upon his leaving India Lord Teignmouth had been s ceeded as president of the Asiatic Society by Sir Rote: Chambers, in a discourse by whom, delivered at a meet of the Society on the 18th of January, 1798, and print. in the sixth volume of their Transactions, there a sketch of the character and career of his predecessor. I 1804, on the formation of the British and Foreign B Society, Lord Teignmouth was elected its first pressur and this situation he retained till his death, though for som years before that event he was obliged to devolve its ***: duties upon his successor, Lord Bexley. In the prospe of the Society he at all times took the liveliest interest On the 4th of April, 1807, Lord Teignmouth was pointed one of the commissioners for the affairs of 1 or, in other words, a member of the Board of Control a on the 8th of the same month he was sworn of the P Council. He retained his seat at the Board of Control some years; and his death took place on the 14th of F bruary, 1834. མ Besides the publications already mentioned, Lord Te mouth is the author of A Letter to the Reverend topher Wordsworth, D.D., on the subject of the B Society,' 8vo., London, 1810; and Considerations communicating to the Inhabitants of India the Know t of Christianity,' 8vo., London, 1811. (Gent. Mugie 1834, pt. i., p. 552.) TEIGNMOUTH, JOHN SHORE, LORD, was the eldest son of Thomas Shore, Esq., sometime of Melton in Suffolk, and of his wife Dorothy (other authorities say Deborah) Shepherd. The family was originally of Derby- TEISSIER, ANTOINE, was born at Montpellier. shire, Lord Teignmouth's great-grandfather having been January, 1632. His family, which was origina v a Sir John Shore, of Derby, M.D., who was knighted in Nîmes, was Protestant; and his father was receive 1667. Lord Teignmouth was born, it is believed, in Devon-neral of the province of Languedoc, but he was depi shire, October 8, 1751: his father died in 1759, his mother in 1783, and his only brother, the Rev. Thomas William Shore, who was vicar of Sandal in Yorkshire, and of Otterton in Devonshire, in 1822. 7 of that appointment, and also of whatever else he p sessed, a few months after the birth of his son, for hav: joined the revolt of Henri, Duc de Montmorenci, a least given up to him the public money which was b Lord Teignmouth went to Bengal in 1769, as a cadet in hands. Montmorenci was taken prisoner at the af the Company's civil service, and was first stationed at of Castelnaudari, on the 1st of September, 1632. Moorshedabad as an assistant under the council of revenue. insurrection was suppressed, and on the 30th of OctIn 1773 his knowledge of that language procured him the ber he was beheaded. After the ruin of his fami appointment of Persian translator and secretary to the was determined that Antoine Teissier should be eProvincial Council of Moorshedabad; and this was fol- cated for the ministry of the Protestant church, alowed the next year by a seat at the Calcutta revenue with that view he studied theology for some time board, which he retained till the dissolution of the board the Protestant seminaries of Nîmes, Montauban, 1 in 1781, when he was appointed second member of the Saumur. But in the end he made up his mid general committee of revenue, established by the new adopt the profession of the law, induced, it s charter granted that year. While holding this situation, by the weak state of his health; and after having Mr. Shore lived in terms of intimacy with Warren Has- through the usual course of study at Bourges, and tac tings, the governor-general; and when Hastings came doctor's degree, he commenced practice as an advə ət home in 1785 he accompanied his friend to England. before the district court called the Presidial, at NuDuring this visit to his native country he married Char- His bodily strength however proved to be no more » lotte, only daughter of James Cornish, Esq., a medical ficient for the bar than it had been thought to be b practitioner at Teignmouth; and a few weeks after, in pulpit; and after some time he gave up his prof April, 1786, he set out again for Calcutta, having been and took to literature as a means of subsistence. appointed one of the members of the Supreme Council revocation of the Edict of Nantes, in 1685, Teissic? "s under the new governor-general Lord Cornwallis. To refuge in Switzerland, having, according to the B his activity and ascendency in the council is mainly phie Universelle,' although in extreme distress, de " attributed the adoption of Cornwallis's great measure, the very tempting proposals which were made through new settlement, in 1789, of landed property in the pre- chancellor D'Aguesseau, to induce him to remain in Fran sidency of Bengal, by which the zemindars, hitherto only But it would no doubt be made a condition th the revenue agents or tax-gatherers of the government, should abjure Protestantism. He supported iss were made the hereditary proprietors of the estates which chiefly at first by publishing a French newspaper at Be they farmed, and the ryots, or peasantry, who had till now then by giving a course of public law droit pubie a right of occupation so long as they paid their assess- Zürich; and the works he sent to the press from tim ments, were declared the tenants of the zemindars, and time also brought him something. At length, in 166 made removable at the will of their landlords. The new was invited by Frederic III., elector of Brander.. judicial system which was introduced towards the close of (afterwards king Frederic I. of Prussia to come to Be Lord Cornwallis's government in 1793, also owed its esta- and there he resided till his death, on the 7th of Sept blishment in a principal degree to Shore, who had been ber, 1715. Immediately on his arrival he had been tol made a baronet the preceding year. On the retirement of nated a councillor of state, and appointed to the office Cornwallis, in August, 1793, Sir John Shore was appointed historiographer; and part of his time was also occ to succeed him as governor-general; and he held that for some years in superintending or directing the d high office till the close of the year 1797, when he resigned | tion of the hereditary prince, afterwards Fredence Wii is I. A complete list o Teissier's numerous publications is given in the Biographie Universelle.' The most celebrated among them is his Eloges des Hommes Savans, tirées de l'Histoire de M. de Thou,' first published at Lyon and at Geneva, in a 12mo. volume, in 1683; then at Utrecht, in 2 vols., in 1696; and again at Leyden, in 4 vols., in 1715. In the two latter editions the text of De Thou is accompanied by numerous annotations, which display much curious research. Teissier was an accurate inquirer; but there is no artistic quality or vital power in any of his books, and all of them, even including his Eloges,' may be said to be now superseded and nearly forgotten. One of the most creditable is a Catalogue, in Latin, of the authors who have written catalogues, indexes, &c., in two parts, 4to., Geneva, 1685 and 1705; some others relate to parts of the history of Prussia; and a great many are translations, which have the character of being generally faithful enough, but of little elegance or spirit, from St. Clement, St. Chrysostom, Calvin, Sleidan, and other Greek and Latin writers, the latter mostly, if not exclusively, moderns. TEIXEIRA. [TEXEIRA.] TEJEN. [PERSIA.] TEJUCO. [BRAZIL, p. 368.] TEJUS. [SAUVEGARDE.] TE'LECLES. [SCULPTURE.] 6 TELEGRAPH (from rλe, distant,' and ypáp,w, 'write"), a machine or contrivance for communicating intelligence to a distance, usually by means of preconcerted signals, to which some conventional meaning is attached. On this account telegraphic communications may be as remarkable for their impenetrable secrecy as for their rapidity. The name semaphore (from nua, a sign,' and pip., bear'), is commonly applied to some of the machines used for effecting telegraphic communication; which, in an extended sense, may be considered to embrace every means of conveying intelligence by gestures and visible signals, as flags, lanterns, rockets, blue-lights, beacon-fires, &c., or by audible signals, as the firing of guns, the blow ing of trumpets, the beating of drums or gongs, &c., as well as by the machines called telegraphs or semaphores. 6 Although telegraphic communication, as a means of conveying any required intelligence, is an invention of recent date, the use of signals for the speedy transmission of such brief messages as might be previously arranged between persons, is a practice derived from the most remote antiquity. The use of beacon-fires, for example, as a means of giving speedy warning of the approach of an enemy, is alluded to by the prophet Jeremiah, who wrote about six centuries before the Christian æra, and who warns the Benjamites to set up a sign of fire in Beth-haccerem ; for evil,' he adds, appeareth out of the north, and great destruction.' (Jeremiah, vi. 1.) The fine description given by Eschylus, in his Agamemnon,' of the application of a line of fire-signals to communicate the intelligence of the fall of Troy, is often referred to as an early instance of this kind of telegraphic despatch; but if the æra of the writer, and not that of the event, is referred to, the passage above quoted affords an earlier illustration. This simple means of spreading an alarm, or communicating intelligence in time of war, is practised by many nations; and, to come nearer home, we may refer to the graphic stanzas of the Lay of the Last Minstrel' (canto iii., st. xxv.-xxix.), descriptive of the rapid communication of the approach of the English forces from the border stations, along height, and hill, and cliff, Till high Dunedin the blazes saw, In a note illustrative of this description, Scott refers to an Act of the Scottish parliament in 1455, c. 48, which directs that one bale or faggot shall be warning of the approach of the English in any manner; two bales, that they are coming indeed; and four bales blazing beside each other, that the enemy are in great force. Such signals, though best adapted to give information by night, were also available in the daytime, when they appeared as columns of dense smoke. Torches held in the hand and moved in any particular manner, or alternately displayed and hidden behind a screen, were also used in antient times as signals, as we learn from several early writers on P. C., No. 1506 military subjects; but as they were merely arbitrary signals, which admitted of very little variation, such devices could only be rendered available by previous concert. That some attempts were made by the antients to improve upon such simple signals is evident from the tenth book of Polybius, in which allusion is made to a device of Eneas (Tacticus), who proposed to write several sentences, such as it might be desirable to communicate, upon two oblong boards, one of which should be kept by each of the parties. These boards were to be affixed to cork floats capable of rising and falling in cylindrical vessels of similar form and size, one of which was placed at each station. Matters being thus prepared, and the vessels filled with water, the person desiring to send intelligence allowed the water to escape from his vessel by a small opening until the suitable sentence on the inscribed board had sunk to a certain mark; making torch signals to indicate the moment of allowing the water to run out, and that at which the board sank to its proper level. The person at the distant station regulated the egress of water from his vessel by the torch signals, and was thus enabled to ascertain which of the sentences written on the board conveyed the required intelligence. Complicated as was this arrangement, it afforded very little more scope than the use of simple torches or files. Polybius however describes a much more perfect method of telegraphic communication, which, he says, was invented either by Cleoxenus or Democlitus, but improved or perfected by himself. This method is capable of communicating any required intelligence with the greatest precision, the signals being made to represent the letters of the alphabet, and the message being displayed letter by letter. Instead of quoting the description of Polybius himself, which refers to the use of the Greek aphabet, we shall adopt that of Bishop Wilkins, who describes the plan as applied to the English alphabet. The alphabet must be divided for this purpose into five portions of five letters each (excepting the last, which has but four, j and being omitted as unnecessary), and inscribed upon tablets, as in the following diagram: a f q 2 b g m This being done, each of the corresponding parties is to be provided with a copy of the tablets, and also with ten torches, five of them on the right hand and five on the left. Any letter may then be expressed by first lifting up on the right hand so many torches as may indicate the number of the tablet in which it is contained, as I., II., III., &c., and then so many on the left as may show the number of the particular letter in the tablet, as 1, 2, 3, &c. Thus the word husten would be expressed by displaying the torches six times, in the following orde in which the Roman letters indicate the number of toes raised on the right hand, and the Arabic numerals on the left: se Fig. 1. T+CIHO LSVAXVAO ox()un four necessary letters of the alphabet are, according to hind the screen by a rope c, passing over pulleys in the this plan, which he gives on the authority of Joachimus frame-work, and so rendered visible in the open space at Fortius, to be divided into three classes of eight letters b. These telegraphs were to be erected upon elevated each. The first class is represented by one torch, the second by two, and the third by three; and the number of the letter by the number of times which the torches are elevated or discovered. Thus one torch raised once would represent a, or raised eight times, h; two torches raised once would indicate i, raised twice, k; or eight times, q; and three torches raised from once to eight times would give the remaining letters, from r to z. Similar to this, but still easier of application, is the night-telegraph contrived by the Rev. James Bremner, of the Shetland Islands, and rewarded by the Society of Arts in 1816. A single light constitutes the whole apparatus in this plan, and the whole operation consists in its alternate exhibition and concealment. The alphabet is divided into four classes or divisions, of six letters each; and the number of ob- stations, so chosen that, if possible, there might be no rescurations is to indicate, first, the number of the division, fraction of the atmosphere to impede vision, and so tha and secondly, the number of the letter in that division; a no intervening objects or disturbed background mig! pause being made between the obscurations which indicate interfere with the clearness of the prospect; and telethe number of the division and those which show the scopes were to be used by the observers. The order of number of the letter in that division; and a longer pause connection between the signs employed and the letters of between the double set of movements thus required for the alphabet might, it is explained, be infinitely vane every letter. Two lights, one to represent the division, for the sake of secrecy; and none of the parties employe and the other the number of the letter, might in some excepting those at the terminal stations, need have any cases be used; but Mr. Bremner conceives that, especially knowledge of the message communicated. Hooke further in long distances, one is preferable, as affording less risk proposed a scheme for night communication by means of error. His plan had been found suitable for distances lights disposed in a certain order. About twenty years of twenty miles and upwards, and had been successfully after the date of Hooke's paper, Amontons brought for put in operation between the lighthouse on Copeland ward a very similar plan in France, and made public tra Island and Port Patrick on the opposite side of the Irish of his contrivance before several persons of rank. Some Channel. Further particulars respecting this, and a de- other individuals subsequently devised similar schemes, scription of another telegraph for day-service, by the same but nothing was effected in the practical application of author, are given in the thirty-fourth volume of the So-telegraphic communication until the war of the French ciety's Transactions,' pp. 213-227. Tedious as Mr. Brem- revolution. Macdonald states that, Following the pr ner's method may appear, it is stated that, supposing the ciples laid down by Dr. Hooke, in 1684, Dupuis, in France, whole alphabet to be used, sixty letters might easily be invented the French telegraph, which Don Gualtier, a given in five minutes; while the communication might monk of the order of Citeaux, in 1781, modified, and probe effected more rapidly if, as in some telegraphic systems, posed to Condorcet, Milli, and Dr. Franklin, who rec only sixteen letters were used. In addition to the alpha- mended it to the French government.' The telegraph betic systems which depend merely upon the number or brought into use in 1793 or 1794, by M. Chappe, was, a alternate display and concealment of lights, Bishop Wil- will be seen by g. 2, a very superior machine to th kins describes one which depends upon the relative posi- of Dr. Hooke. tions of two lights attached to long poles, and which, he says, for its quickness and speed is much to be preferred before any of the rest.' It will thus be perceived that that ingenious writer came very near to the principle upon which many of the modern telegraphic systems depend. In suggesting the use of extended lines of telegraphic communication, he further hints at the application of the telescope (or, as he styles it, 'Galileus his perspective'), to the deciphering of distant signals. Fig. 2. TTTTT イイ イイイ Among the scientific writers who seem to have had some notion of the modern telegraph are Kircher, Schottus, and Kessler; the latter of whom proposed to cut out such characters as it was desired to show in the ends of a cask, which was to be elevated with a light enclosed in it. The Marquis of Worcester also, in his Century of Inventions,' 1663, announces, How at a window, as far as the eye can discover black from white, a man may hold discourse with Chappe's telegraph, which, from its position when at his correspondent, without noise made or notice taken,' rest, is sometimes called the T telegraph, consisted of an &c.; and again, A way to do it by night as well as by upright pole or post, at the top of which was pivoted, ly day, though as dark as pitch is black. The earliest well- its centre, a transverse beam, which, by means of ropes defined plan of telegraphic communication appears how- i worked in the chamber below, that served also for a ever to be that described in a paper addressed to the servatory, might be made to assume any required an Royal Society in 1684, by Dr. Robert Hooke, and pub-with the post. Each end of this moveable beam cara lished in 1726 in Derham's collection of his Philosophical a short arm, that was capable of assuming any required Experiments and Observations,' pp. 142-150, showing a angle with it; and these arms also were worked by ropes way how to communicate one's mind at great distances.' which were conducted through the axis of the team. Hooke states that he had discoursed on the subject some order that the necessary degree of tension might not b years before, but that the then recent siege of Vienna by disturbed by the action of the machine. By this e the Turks had revived the matter in his mind. His scheme trivance, without the use of any angles of less than 45 will be readily understood by the annexed cut, Fig. 1, (which might be indistinct when viewed from a great diwhich represents an elevated frame-work supporting a tance, or under the influence of a refractive atmosphere. panel or screen, a, behind which were to be suspended a as many as 256 different signs might be made. Amrh number of symbols or devices, formed of deal plank, of the smaller number was however sufficient, as M. Chappe various shapes represented by the small black figures. communicated his intelligence letter by letter, and siThe first twenty-four of these, which consist entirely of plified the movements by using an alphabet of only sixstraight lines, were to stand for alphabetic characters; and teen letters. The small figures in the cut show scite of the six devices consisting of curved lines were to be used the different positions assumed by the beam and a as arbitrary signals. Whenever it was desired to display and, as the connection between these and the letters they any of these characters, they were to be drawn from be- were made to represent was quite arbitrary, their significa |