dry ditch and a thick mud wall, flanked at intervals with semicircular projections, and pierced by gates which are always guarded, and are closed after sunset. Inside there are many vacant spaces, gardens, and extensive ruins; but the streets are narrow, irregular, unpaved, and filthy. The houses are badly built and mean in appearance. Outside the walls are suburbs of considerable extent, several large caravansaries, and many enclosed gardens. The principal building of the town is the Ark or royal palace, which occupies a large space adjoining the northern wall, and is fortified. The bazaars are wretchedly kept and dirty. One of the mosques is roofed with plates of gold. In summer the climate is unhealthy, and the monarch and about two thirds of the inhabitants encamp on the plains of Sultanieh. On a hill in the neighborhood the shah has a palace and beautiful gardens. Telegraph wires connect Teheran with the Caucasian and Turkish frontiers. Not far from it are the ruins of the ancient Rhages, the capital of Parthia. Teheran was unimportant until made the capital of Persia by Aga Mohammed Khan about 1796. A treaty of commerce with England was signed here, Oct. 28, 1841.

but resigned in September on account of his support of the new liberal constitution, in op position to President Comonfort. He was a member and thrice the president of the house of representatives during the sessions of 1861-22. He opposed the treaty for arranging the English debt, and its failure led to the downfall of the Zamacona cabinet. His influence led to the ratification in December, 1861, of treaties of commerce and of extradition with the United States. He was member of congress in 1862-'3, and followed the government on its removal from Mexico, during the French invasion. On Sept. 2, 1863, he became minister of justice, and on Sept. 11 of foreign affairs. He shared with Juarez the honor of the eventual recovery of the national independence. The presidential term of Juarez expiring on Nov. 30, 1865, Lerdo de Tejada, to avert the excitement of a new election, caused the presidential term to be extended until the termination of the war. After the capture of Maximilian, he was vainly solicited to spare his life. After the return of Juarez to the capital, in July, 1867, Lerdo de Tejada suspended all treaties with those foreign powers which had failed in neutrality toward Mexico, or had joined in the intervention; but he accorded to aliens the same security as to Mexicans. In 1868 he became chief justice of the supreme court. In that capacity, under the constitution, he became president on the death of Juarez in July, 1872; and on Nov. 1 he was almost unanimously elected to that office for the term ending Nov. 30, 1876.

TELEGRAPH (Gr. The, afar, and ypaper, to write), an apparatus by which intelligence is communicated to a distance. It properly includes the various methods of signalling. The Roman generals, as described by Julius Africanus, spelled words by means of fires of different substances. The North American abo

TEHUANTEPEC. I. An isthmus of Mexico, lying between the bay of Campeachy on the gulf and the bay of Tehuantepec on the Pacific, and comprising the states of Tabasco and Chiapas and parts of Vera Cruz and Oajaca. Its breadth from bay to bay, at the narrowest place, is 130 m. It is drained by the Coatzacoalcos river, which flows northward, discharging into the bay of Campeachy, and extending three fourths of the width of the isthmus; and by the Tehuantepec river, flowing into the bay of the same name. There are several lakes and lagoons. At one time it was proposed to construct a ship canal across the isthmus, improving the navigation of the Coat-rigines made use of regular stations over the zacoalcos for a part of the distance, and surveys were made. (See CANAL, vol. iii., p. 690.) II. A town of the state of Oajaca, on Tehuantepec river, about 15 m. above its mouth, and 110 m. E. S. E. of Oajaca; pop. about 14,000. The houses are generally of stone. Part of the town is occupied by Indians, who are civilized and industrious. It has salt works and cotton factories, and a considerable pearl fishery in which many of the inhabitants are engaged. Indigo is raised in the vicinity, a purple dye is procured from a shell fish abundant there, and some cochineal is exported. The harbor is shallow, with a dangerous bar at the mouth of the river, and is little frequented.

TEJADA, or Lerdo de Tejada, Sebastian, president of Mexico, born in Jalapa, April 25, 1825. He was educated in the seminary of Puebla and in the college of San Ildefonso, in the city of Mexico, became rector of the college in 1852, and received the diploma of advocate in 1853. He was a judge of the supreme court from December, 1855, to June 1, 1857, when he became minister of foreign affairs and premier,

western country for such signals; and the Indians of the northwest territory in this way made known the approach of Fremont, as he passed through their regions. Polybius describes two modes of telegraphing by means of torches; and Bishop Wilkins, after giving an account of this in his book entitled "Mercury, or the Secret and Swift Messenger," describes a method of conversing at a distance with three lights or torches at night, which may be so used as to indicate the 24 necessary letters of the alphabet, these being divided into three classes of eight letters each, which are severally designated by one, two, or three torches, and the number of the letter by the number of times the torches are elevated or displayed. Another method was also proposed by Bishop Wilkins, in which intelligible signals were conveyed by means of two lights attached to long poles; and for long distances he suggested the use of the then newly invented telescope. A variety of systems of telegraphic signals were brought into notice by different inventors in the 17th and 18th centuries, one

on.

of the earliest of which is that of Dr. Robert | modifications of this apparatus were used. Hooke described in the "Philosophical Trans- For telegraphic communication at sea, flags actions" for 1684. It consisted of 24 symbols formed of blocks of wood, representing alphabetic characters, and six more formed of curved lines to be used as arbitrary signals. These were to be exposed in succession in an elevated frame at some conspicuous point, and, being observed at another station, were to be there repeated and sent forward to the next, and so At night torches or other lights were to be substituted for the wooden figures. The first working telegraph of much importance was that known as Chappe's, invented in 1792, which was brought into use during the wars of the French revolution. At the top of a tall post was attached a cross bar upon a pivot, so that it could be easily turned from a horizontal to an inclined position. Each end of this cross bar carried a short arm, which could also be turned upon its pivot so as to stand in any position in relation to the bar. The movements were made by means of ropes which passed through the bar and down the post. This apparatus admitted of 256 distinct signals; but M. Chappe limited its use in great part to 16 signals, each one of which represented a letter of the abbreviated alphabet he had constructed. Chappe's method has been generally adopted, all the alleged improvements in it being of minor importance. Mr. R. Lovell Edgeworth about the same time brought before the public his plan of a telegraph, or as he called it telelograph or tellograph, by which the signals represented numbers, the meaning of which would be found in the dictionary prepared for this system. The signals were made by means of four pieces of wood, each one in the form of a long isosceles triangle, placed near together, cach supported upon a pivot round which it could be turned in any direction. The movements of each were limited to eight, and indicated the first seven numerals and zero. The first triangle or pointer represented units, the second tens, the third hundreds, and the fourth thousands, so that any number might be expressed that did not contain the figure 8 or 9. The admiralty telegraph proposed by Lord G. Murray was used in England from 1795 to 1816, when it gave place to that known as the semaphore (Gr. oua, a sign, and pepew, to carry), which the French had adopted in 1803. This consisted of six conspicuous boards or shutters set in a frame, each of which could be turned upon its axis so as to present either its edge or its broad surface to the next station. The movements represented figures, and a series of numbers was indicated by their combinations. Some of these stood for the letters of the alphabet, and the others for arbitrary signals. The French semaphore (also known as signal posts) consisted of three or more arms attached by pivots to an upright post, admitting of motion in any direction, and indicating by their various positions either figures or letters. Many

of various colors have long been used. (See SIGNALS, NAVAL.) In 1835 Gauss proposed to employ a small heliotrope or mirror for reflecting rays of light from the sun or an artificial source as a means of communicating signals. With a mirror so small that it may be carried in the waistcoat pocket, flashes of light may be clearly perceived for 12 m. or more, and, the mirror being gently moved on some established system, the appearance and disappearance of the flashes may indicate letters or words. By this device time can be saved, telescopes dispensed with, and the signals seen only by those for whom they are intended. Francis Galton, the African traveller, proposed a plan similar to this at a meeting of the royal geographical society, and described an optical arrangement he had devised by which the operator may know if the mirror is directed aright. Among the later publications upon the telegraphs adopted previous to the electric telegraph, are papers in the "Journal of the Society of Arts," vols. xxvi., xxxiv., xxxv., and xxxvi.; "A Treatise explanatory of a new System of Naval, Military, and Political Telegraphic Communications," &c., by John Macdonald (London, 1817); "Description of the Universal Telegraph for Day and Night Signals," by C. W. Pasley (London, 1823); and Edgeworth's "Essay on the Art of conveying Secret and Swift Intelligence," in the "Transactions of the Royal Irish Academy," vol. vi. The advantage of all these methods of telegraphing, which may be described in general as the optical method, is, that they employ nature's great highways, which cost nothing; the disadvantages are, that the signals cannot record themselves, but require the constant attention of an observer, and can be used only for moderate distances and in favorable weather. Moreover, the expense is great compared with the meagre intelligence which is communicated. The semaphore between London and Portsmouth, 72 m., which could be used less than one fifth of the time, required an annual expenditure of £3,403.-ELECTRIC TELEGRAPH. The various kinds of electric telegraphs may be classified in two ways. In the first place, they differ in regard to the source from which the electricity is derived. In the present state of science, five independent sources of electricity are recognized: 1, friction; 2, chemical action; 3, magnetic induction; 4, heat; 5, physiological actions. The difficulty of insulation unfits frictional electricity for this work, except at short distances and in dry air. The fourth and fifth sources must be rejected as insufficient for practical use. Successful telegraphs must rely on electricity produced by chemical action or magnetic induction. In the second place, electric telegraphs may be classified according to that one of the five special effects of electricity which is selected as the means of delivering the message when

another, and thus two letters were indicated. | and thence passed to the first station. EventuSömmering found that the addition of 2,000 ally he succeeded in reducing the number of ft. of wire produced little or no sensible addi- needles to one. He also introduced an alarum tional resistance, and that voltaic action was at the commencement of the passage of the instantaneously developed at least for the dis- current by causing a solid body to fall, on the tance of 3,000 ft. In 1810 Prof. Coxe of Penn- same principle as had been already recomsylvania suggested a method of telegraphing mended by Prof. Henry in his lectures. These by means of the chemical effect of electricity. experiments were interrupted by his death, Schweigger described an improvement upon and the steps made were lost, without even a Sömmering's arrangement, by which all the very accurate account of the results being prewires could be dispensed with except two. The served. The next experiments of importance batteries then known were insufficient for the were those of Gauss and Weber of Göttingen transmission of currents through great dis- in 1833 and 1834. They employed first voltaic tances, and besides were deficient in sustain- electricity excited by numerous small elements, ing power; therefore no further progress was and afterward a magneto-electric machine to made in perfecting the electric telegraph until transmit signals from 9,000 to 15,000 ft. They the principles of electro-magnetism had been caused a magnetic bar to be deflected to one developed. (See ELECTRO-MAGNETISM.) In 1819 side or the other, and interpreted its repeated Oersted discovered the power which the cur- movements into the letters of the alphabet. rent possesses of deflecting a magnetized nee- The vibrations of the magnet were checked by dle out of the magnetic meridian. In 1820 a damper, or by the use of currents alternating Schweigger added the multiplier. This was in direction. This telegraph was of practical followed by Arago's discovery in the same value in comparing clocks and for other puryear that a steel rod was magnetized when poses. Gauss stimulated his pupil Steinheil to placed across a wire which was carrying a a bolder undertaking, in which he was ascurrent. Ampère immediately substituted a sisted by the Bavarian government. Steinhelix for a straight wire. In 1825 Sturgeon heil's telegraph, completed in 1837, extendused soft iron in place of steel, and the electro- ed 12 m., employed but a single wire, and magnet was born. Between 1828 and 1830 made use of the earth to complete the circuit. Prof. Henry of Princeton, N. J., made great The signals were sounds produced upon a series improvements in the construction of electro- of bells of different tones, which soon became magnets by covering the wire and winding the intelligible to a cultivated ear; and the same coil compactly. In 1831 he devised an instru- deflections of the needle that caused the sounds ment which is essentially the same as the were also made to trace with ink lines and dots Morse register. Moreover, Ohm in 1827, and upon a ribbon of paper moved at a uniform Fechner in 1831, published the results of their rate, the alphabet having a remote resemblance theoretical investigations into the laws of the to that invented by Swaim in 1829. Steinheil voltaic current, which shed a flood of light on used a magneto-electric machine, but with the the subject of telegraphing at long distances. magnets stationary and the multiplying coils If these investigations had but little practical revolving close to them.-Morse's telegraph, effect, it was because they were not generally which is generally recognized in all parts of known until the same results had been at a the world as the most efficient and simple, was later day worked out empirically. Equally first publicly exhibited in the university of important was the invention of the constant New York in 1837. It had been gradually battery by Daniell in 1836, and of various brought to a working condition by experiother constant batteries which have been con- ments and contrivances devised by the inventor trived since that time. The discovery of mag- since 1832, with the assistance of L. D. Gale neto-electricity by Faraday in 1831, and the and George and Alfred Vail. In October, introduction at a much later date of the induc- 1837, Prof. Morse filed a caveat in the patent tion coil, supplied constant sources of intense office to secure his invention; and he obtained electricity adapted to the telegraph. Within a the patent in 1840, covering the improvements year after Oersted's discovery Ampère pointed he had in the mean time made in the apparatus. out its applicability to telegraphic signals. The telegraph was first brought into practical His plan contemplated at least 30 needles and use, May 27, 1844, between Washington and 60 independent wires. In 1828 Ritchie gave Baltimore. An insulated wire buried in a lead an experimental illustration of such a device pipe underground was first tried, and failing before the royal institution of London. In was replaced with one on posts. The power was 1829 Fechner had a similar project for uniting derived from a voltaic battery, and an electroLeipsic and Dresden by means of 24 sets of magnet was employed at the receiving station underground wires. In 1832 Schilling ex- for developing its effects. When the current hibited to the emperor Nicholas of Russia a flowed, this magnet attracted an armature, by needle telegraph in operation on a small scale. which, according to the duration of the curHe used a needle provided with a multiplier of rent, dots or lines were marked upon a moving insulated wire for each letter or number to be slip of paper with a pen or pencil. The appaindicated. The several wires were brought to- ratus furnished a simple and effective means gether beyond the multipliers into one cord, of recording signals, which by the needle tele

graph were only evanescent. The apparatus | The armature, A, is attracted by the electrowas improved by the substitution of a sharp magnet M, causing the lever L to vibrate bepoint for the pen or pencil, which is attached tween the screws S S, which are so adjusted to one end of a lever, at the other end of as to limit the vibrations. The backward and which is the movable armature. The following illustrations exhibit the several parts of the Morse instrument as now in use. The key, fig. 1, consists of a brass lever L, swung on pivots, and having on one end a button. When this button is pressed down, two platinum wires, a and b, are brought into contact, thus closing the circuit; when the pressure is removed, a spring lifts the lever, separates the wires, and breaks the circuit. When the message is sent the operator permanently closes

FIG. 8.-Sounder.

forward blows thus given, some of which are short and some long, correspond to the dots and dashes of the Morse alphabet. This is now more generally used than the Morse register or recording instrument, as experience has proved that fewer errors are made by the ear than by the eye. The Morse register, fig. 4, has also the electro-magnet M, the armature A, the lever L, and the adjusting screws SS; but instead of producing sounds merely, the lever L embosses on a fillet of paper P dots and dashes in precise accordance with the movements of the key and relay. The paper is carried between two rollers, moved by clockwork, in one of which is a groove, into which the steel point presses the paper. When successive blows are struck on the key, closing and opening the circuit quickly, corresponding dots appear on the paper; but if the key be pressed down for a longer or shorter time, keeping the circuit closed, a continuous line of any desired length may be produced on the paper. The signs for the letters of the English alphabet

FIG. 2.-Relay.

current and becomes magnetized and demagnetized. The delicately poised lever L, having the armature of the magnet attached to it, vibrates forward and backward, bringing together the two platinum wires a b, and thus breaking and closing a secondary or local circuit, embracing a local battery and a strong electro-magnet. This magnet performs various work, such as embossing or printing paper, or the liberation of machinery for the production of sounds. A screw B is used to move the magnet coils backward and forward so as to adjust the general magnetic power, and a spring S retracts the armature after magnetic attraction has drawn it forward. The sounder, fig. 3, is an electro-magnet used in the local circuit.

(which are variously modified to adapt them to other alphabets), and for the numerals and punctuation marks, are as follows, those most used being the simplest: