electric force to accomplish its work may be transmitted through the wire for long distances (as has occurred between New York and Boston), with the wire actually lying upon the ground during a heavy rain storm. So little power is required to work it under ordinary circumstances, that 10 cups of the Grove battery have been found sufficient between Boston and New York. This telegraph, like most of the others excepting the Morse, requires an alarum bell to call the attention of the operator when a message is to be sent from another station, and for this an electro-magnet is employed distinct from the registering apparatus. Mr. Bain made many other inventions in the telegraph, several of which are too remarkable to be passed over. One of these, adapted for transmitting words at the extraordinary rate of 5,000 per hour, employed at the sending station narrow strips of paper perforated with holes and elongated slits, making the message in these regular characters of the system. These strips (prepared beforehand) were passed in succession over a cylinder of metal with a pin connected with the wire so placed as to press lightly upon the paper and enter each hole as it passed along and complete through it the circuit. At the other station similar strips of chemically prepared paper were passed at precisely the same rate under the same sort of style as that just described, and colored marks were thus produced exactly corresponding to the holes in the paper at the transmitting station. The advantage of this system is in the transmission of very long messages which may be prepared in separate parts by a number of operators; or, as is now done, by the use of a very ingenious machine which perforates the paper with great rapidity, as it is worked by striking keys like those of a piano. The difficulty in the practical application of this telegraph appears to be the want of some efficient means of exactly regulating the speed of the apparatus. The universal telegraph of Prof. Wheatstone, recently introduced in London, is based on this principle. Another of his inventions was a printing telegraph, in which types arranged around the periphery of a wheel were brought successively opposite the face of a cylinder covered with paper and instantly pressed against it, while the cylinder turned at a regulated speed around its axis, and at the same time was carried longitudinally along it so that the printed lines passed in spirals from one end of the cylinder to the other. The electric current caused the rotation of the wheel having the types, and also stopped or liberated the other movements which depended upon springs and clockwork. The machines at the different stations are precisely alike, and all their movements are perfectly synchronous. A printing telegraph of somewhat similar construction was invented in 1837 by Mr. Alfred Vail of New York; and others have been produced by M. Froment in France, Royal E. House of Vermont, David E. Hughes of Kentucky, and Jacob Brett in Great

Britain. Some of these will be noticed further on. An electric copying telegraph was invented by Mr. F. C. Bakewell of England in 1850, designed for giving an exact copy of the message sent. This is written with a pen dipped in varnish upon a sheet of tin foil, which is then laid around a metallic cylinder, corresponding precisely in its size, rate of revolution, and longitudinal movement, with another cylinder at the receiving station, which is covered with chemically prepared paper and provided with an index like that of the Bain chemical telegraph. These cylinders being set in motion at the same instant, the index of the registering apparatus makes a continuous colored line, running round the cylinder in a close spiral so long as the metal style at the other station presses upon the tin foil; but as this passes over the lines of varnish a break in the circuit occurs, causing an interruption of the colored line at the other station. The blank spaces thus produced will be found when the lines have been drawn over the whole paper to be a facsimile of those written in varnish upon the tin foil. The lines, though drawn as spirals upon a cylinder, appear as parallels when the paper is taken off. About 10 revolutions of the cylinder, making as many parallel lines, are sufficient to complete one line of writing; cylinder 6 inches in diameter affords sufficient length for about 100 letters of the alphabet in one line; and as the rate of revolution is not less than 30 in a minute, 300 letters or more may be transmitted in this period. A message in cipher can be sent by this method without risk of error, and even invisible messages written in colorless varnish may be received and impressed in invisible characters upon prepared paper, to be afterward brought out by chemical means; thus, if the paper be moistened with diluted acid alone, no visible mark is left upon it until it is brushed over with a solution of prussiate of potash, when the lines appear in their blue color. The patent for the House printing telegraph was issued by the U. S. patent office in 1848, but bears date April 18, 1846, when it was first applied for. It was with this apparatus that the first printed despatch ever produced upon a telegraph line was sent, in the autumn of 1847, from Cincinnati to Jeffersonville, opposite Louisville, Ky., 150 m. The system is regarded as one of the most wonderful and complete of the extraordinary inventions developed by the telegraph. The necessity of avoiding the peculiar features upon which other telegraphic systems were established, in order to give to it a distinctive and patentable character, added greatly to the difficulties of the undertaking, which however were after nearly 6 years of labor overcome by the ingenuity and perseverance of Mr. House. The apparatus is too complicated for any description of it to be made intelligible without illustrations, and little more can be attempted than to state its great powers of execution and its perfect accuracy.

The mechanical move

ments of this machine are set in action by hand labor applied to a crank, which works an air pump for the purpose of supplying a current of condensed air, which under the control of the electric current carries forward the movements of the composing and printing apparatus, so that each letter may be printed at the exact instant that it is struck upon the key-board of the instrumeut. This key-board, which resembles that of a piano, is connected with the electric current, and as the keys are struck the circuit is opened and closed with the movements of a circuit wheel which controls the movements of the type wheel. A complete revolution of the circuit wheel, coming round again to the same letter, breaks and closes the circuit 28 times, and other letters a less number according to their arrangement on the type wheel. The printing apparatus is quite distinct from the circuit, but the composing apparatus forms a part of it. The impression of the letter is produced by a blackened ribbon being pressed against the paper by the type. From the galvanic battery of one station, the current passes along the wire to the next station, then through the coil of an axial magnet to the insulated iron frame of the composing machine, and thence to a circuit wheel revolving in this frame. Through a spring that rubs on the edge of this wheel it passes into the return wire, and through another battery back to the first station to pursue the same course through the composing machine and magnet there and all others upon the line. In sending a message, the operator sets his machine in motion and gives a signal by breaks of the circuit, repeated a different number of times for different offices on the same wire. As this is heard by the operator at the receiving station, he sets his machine in motion, and the type wheel at its starting point, and signals back that he is ready. No further attention is required on his part, while the machine goes on, printing in Roman capitals the communication upon the long strip of paper regularly supplied to the type wheel. Two hundred and fifty to 260 letters as a maximum can be accurately printed every minute, and over 3,000 words an hour of press news, partly abbreviated, have been sent over the wires with a single instrument.The inventions of Mr. Hughes, patented May 20, 1856, showed that the field of discovery in telegraphing was far from being exhausted, by introducing apparatus even more wonderful in its operation than any which had yet preceded it. His was a printing telegraph, in which the feat of printing a letter with every impulse or wave of the electric current was accomplished. In the other telegraphs, as already described, several impulses produced by successive closings or breaks of the circuit are required to form a single letter; this in House's telegraph varies up to 14 breaks, the maximum required for repeating the same letter, and averages about 7 impulses; and in the Morse system the average is about 3 impulses, some of which making lines

are of longer duration than those making merely dots. The saving of time thus effected is of great importance, especially on long lines in which an appreciable amount of time is expended in the passage of the current. In long lines of submarine telegraphs, as will be noticed below, a greatly increased resistance is experienced in charging the wires with the electric current, and the impulses necessarily succeed each other with extreme slowness and diminution of force. The type wheel in the Hughes system is provided with 28 types; it is kept in rapid revolution during the whole time of operating, and is so perfect in its movement, that though the revolutions may be from 100 to 140 per minute, the variations of two machines at different stations do not exceed of a second in several hours' running. At the instant one of the 28 keys of the key-board, which is like that of the House telegraph, is depressed, the current entering the magnet at the distant station causes the strip of paper to be brought against the type opposite to it at the time, and receive the impression in ink while this is rapidly carried round with the wheel. The operator can send an average of two impulses with each revolution of the type wheel, thus making the capacity of the instrument full 200 letters or 40 words per minute, and the maximum is much above this. The regulators or governors of the clockwork which carries the type wheels at the different stations are of an entirely novel character. These are springs of the same musical tone, which consequently vibrate the same number of times per second, and which control by their vibrations the escapement of the apparatus. The power of the electric current required is reduced in a wonderful degree by the combination of the natural magnet and the electro-magnet, making only so much electricity necessary as will neutralize the magnetism in the natural magnet by causing magnetism of an opposite polarity to be created in the poles of the electro-magnet. This extreme delicacy, however, renders the telegraph liable to be interrupted by atmospheric electricity, such as is developed previous to and during the continuance of the aurora borealis. It is asserted that this instrument can work upon a longer line without the aid of repeaters than any other, and this with an extraordinarily low battery power.-In the winter of 1858 a new instrument was perfected by G. M. Phelps of Troy, combining the most valuable portions of both the House and Hughes patents, and which has been introduced with great success on nearly all the lines formerly using those inventions. This has appropriately been termed the "combination" instrument, and has the advantage of being able to work through a much longer circuit than the House machine, with a smaller battery, as well as of being much simpler in construction. The keyboard and transmitting machinery of this instrument are precisely like those of Hughes, as is also the printing apparatus, with the excep

tion of the electro-magnet, which is of the ordinary form, and operates upon the type wheel through the medium of compressed air as in the House machine. The vibrating spring used by Hughes as a governor is superseded in the combination instrument by a most ingenious electro-magnetic governor, the invention of Mr. Phelps. It consists of a hollow iron drum, geared to the transmitting cylinder and type wheel of the instrument and moving with them, but much faster. If the machinery has a tendency to revolve too rapidly, the increased centrifugal force, acting upon a detached section of the drum, actuates a series of levers inside, by which a spring is raised, closing the circuit of a local battery through an electro-magnet. A friction brake, which is applied to the revolving drum by the attraction of this magnet, instantly reduces the speed to the required limits, when the local circuit is again broken. The combination is considered to be the most perfect printing instrument yet produced. Among the several telegraphs employed in England, those of the "Magnetic Telegraph Company" are worked by magneto-electricity, thus dispensing with voltaic batteries, the use of which involves much care and expense. The apparatus is remarkably compact, without clockwork or complicated movements such as are common in other telegraphs. Though used double with two sets of magnets, with a wire from each connecting with two needles upon the dial at the opposite station, the whole apparatus including the tablet or dial occupies but a few inches space, and is always ready for instant use, however long it may have remained inactive. The magnets, of horse-shoe form, about 12 in number for each set, are about 15 inches long and 1 broad. They are laid one upon another in two piles near together, and fastened down to the table by screws. Opposite the ends of each pile, placed upon a rotating axis, is the soft iron armature, consisting of two cylinders wound around with long coils of fine copper wire covered with cotton. The wire of the two coils is connected together, and one end of each passes in a spiral through the axle to the platform upon which the apparatus rests. One end is thence carried into the earth, and the other goes to the electro-magnet of its own dial, thence to the distant station, and through the instrument there into the earth. The same arrangement is repeated with the other set. The axis of each armature extends toward the operator, and is provided with a crank handle by which each is turned to generate the electric current. The effect is seen in the movement of the two needles placed upon the dial over the magnets. It is asserted that this telegraph is worked with the greatest economy, that it cannot be disturbed by electric storms in the atmosphere, and that its average celerity has been found to be 27 words per minute, with a maximum of 37.-Telegraph wires are carried over the surface of the country supported upon poles standing 25 to 30

feet above the ground, and placed from 80 to 100 yards apart. If made of red cedar or locust and about 10 inches diameter at the base, they may in general be depended upon for 30 or 40 years; but some poles decay in 3 or 4 years. The durability of other woods may be increased by thoroughly coating them with coal tar. In Europe it is common to saturate the wood with some of the chemical preparations noticed in PRESERVATION OF WOOD. In crossing rivers, where, on account of the swiftness of the current or the danger of disturbance from drift wood, ice, or the anchors of vessels, an insulated wire could not safely rest upon the bottom, masts are erected on the opposite shores, sufficiently high for the wire suspended between them to be above the reach of the masts of boats and vessels that navigate the stream. The longest span in Europe is one of 1,700 feet over the Niemen river at Kovno, in Lithuania. In the United States there are many much longer crossings. That formerly used over the Hudson river at Fort Lee was of 2,700 feet; but the river is now crossed from the foot of 14th street to Hoboken by 6 sunken cables, each having 3 conductors. The Mississippi is crossed at St. Louis in two spans, one of 2,700 and one of 2,200 feet; and near Cape Girardeau, 2,980 feet, from a mast on the Illinois shore 210 feet high to one on the Missouri shore 205 feet high, from a base 110 feet above the water. The Ohio at Paducah is crossed in two spans, one of 2,400 and one of 3,720 feet. At the last named point, on the Kentucky side, the mast is 307 feet high above a bank 32 feet from the water; on the island in the river is a mast 205 feet high, and on the Illinois shore is one 215 feet high. Such masts require strong bracing to bear the strain of the wire with so long a leverage, and resist the action of the winds. The wire employed in these crossings is of iron known as No. 16, and weighs about 63 lbs. to the mile. Sunken cables are fast taking the place of all such river crossings. The ordinary telegraph poles require to be of sufficient strength to sustain a weight of over 400 lbs. suspended upon the wire between them, and at corners they should be still stronger. The following table represents the common numbers of iron wire used for this purpose and its strength, as plain wire, and also when coated with zinc, the figures representing in pounds the strain at which each kind broke. The American wire is stronger than the English, and about equal in this respect to the Swedish:

usually divided at some intermediate point into two distinct circuits, which are connected by means of a "repeater." This operates as a double relay, so that if the circuit be broken on either side of the repeater, it will break the circuit on the other side also. The combined circuits can thus be operated from either end as if they were one continuous wire, while the current of each battery has to pass only half the distance between the terminal stations. A line can thus be extended indefinitely by interposing repeaters at proper intervals and dividing it into a number of separate circuits. Copper wire is a much better conductor than one of iron of the same size, and would carry the electric current from 5 to 6 times as far; but want of strength, and frequent breakage from its greater expansion and contraction by the changes of temperature, prevent its use except on important submarine lines.-Upon some telegraph lines in Europe and in Asia, the wires, instead of being supported upon poles, are buried beneath the ground. Their first cost is always heavy, and many of them have soon proved failures through imperfection in the insulation of the wires, and sometimes from settling in the ground. The wires are best insulated by coating them with gutta percha, and they are protected from injury by laying them in pipes of lead or of earthenware, or in wooden boxes preserved by saturating the wood with a solution of sulphate of copper or chloride of zinc. Some of these lines have worked perfectly well for many years, but when they fail it is a matter of great expense and difficulty to discover their defective points. The insulation of the wires upon the posts is a matter of much importance, and is not easily effected, for any non-conducting substance interposed between the wire and the post becomes a conductor when its surface is wet with rain. Glass knobs with grooves around them for securing the wire have been made of a great variety of forms, and secured to the posts, or to the cross bars where these are to carry several wires, by pins of wood or iron. A great improvement upon this is a glass cap exactly fitting over a wooden pin 14 inches in diameter, and having an outer covering of wood, saturated like the pin with coal tar and pitch, to which the wire is fastened, and which, projecting below and entirely covering the glass, keeps it dry and makes the insulation complete. Hard rubber insulators have been very extensively applied in the northern states during the past five years. The devices in use in different countries for this purpose are very numerous. In forests the wires should be allowed to pass loosely through the supports, so that in case of a tree falling upon. them they need not be broken; but in an open country they are usually fastened to each post. The wires are tightly strained as they are set and secured to the posts; and after the work is completed they require to be frequently looked after by attendants designated repairers, who follow the line and connect the wires when

broken by drawing the ends together and soldering them. These men are often expert operators, and it is narrated of some of those employed in the United States, and familiar with the Morse system, that they can receive intelligible communications through the impressions made by the electric current upon the tongue when the two wires are placed one above and one beneath it.-In the extent of its telegraphic lines the United States has exceeded every other country. In 1860 it was estimated that there were over 50,000 m. in operation; and since that time the number has been largely increased by the completion of the line from St. Louis to San Francisco, which was opened Oct. 25, 1861, and thence to Oregon. In New York city a great number of lines are concentrated, and the following will convey some idea of the extent of the business carried on by the associated companies in their building situated at the corner of Broadway and Liberty street. The basement contains the "delivery" department and the supply department or storeroom, where all materials and instruments used on the lines are kept on hand to be used as required. On the first floor is the department for the reception of messages, in the rear of which is the operating room of the American company, a spacious apartment containing 25 instruments, each arranged on its own table. The wires enter at the rear of the room, and pass to a "switch," which is so arranged that any instrument in the room may at pleasure be instantly placed in connection with any line entering the office. From the switch wires are conducted separately to each instrument. On the second floor are rooms occupied by the president, secretary, and other principal officers of the company. The third floor contains the operating room of the New York and Buffalo and Erie lines. The rooms of the associated press are on the fourth, and the battery room on the fifth floor. In the latter room are some 375 cells of Grove's battery, from which all the lines are supplied with their electric current.

It is estimated that in Great Britain and Ireland there are 40,000 m. of telegraph; in Germany, 35,000; in France, 26,000; in Russia, 12,000; in Italy, 6,600; in Switzerland, 2,000; in Denmark and Sweden, 2,000; in Turkey and Greece, 500. In Australia it is believed there are about 1,000 m. completed, and in India over 5,000 m. controlled by the East India company. The Russians are engaged in extending a very important line from Moscow to the Pacific, which will thus connect eastern Asia with the countries of Europe, and eventually by Behring's straits with the American continent. This line was completed to Perm on the borders of Siberia, and thence over the Ural mountains to Omsk on the Irtish, in 1861; thence it is to be continued to Tomsk, and S. E. to Irkootsk, the capital of Eastern Siberia. It will then cross the Altai mountains to Kiakhta on the Chinese frontier, and then to Cheta on the Amoor. It will then cross to Nertchinsk, to

which point it is to be completed in 1863. From Oroum or some other point on the Amoor one branch will extend down the river, and another toward the S. to a Russian port on the Japan sea. The route from the mouth of the Amoor toward the American continent may be by a short submarine cable to the island of Saghalien and the whole length of the island to its southern extremity, and by a submarine cable to the island of Yesso, and thence by a succession of cables and short land lines through the Koorile islands to the S. point of Kamtchatka; thence along the E. coast by Petropavlovsk to a point opposite Behring's island. By another series of cables and land lines the telegraph will then be extended by the Aleutian islands to America. These islands are inhabited, and the line through them is doubtless much more practicable than by Behring's straits. The longest cable required will not, it is supposed, exceed 200 m. From Russian America to Oregon the intervening space is about 1,700 m., and on the Asiatic side from the straits to the mouth of the Amoor the distance is about 2,200 m. It is believed that the cost of making this connection, unless more serious difficulties are encountered with the savage tribes than is apprehended, will not exceed the cost of the Atlantic cable which was laid in 1858.—The applications of the telegraph have been extended to purposes never anticipated by those who have been most instrumental in establishing it. In 1852 Dr. William F. Channing and Moses G. Farmer of Boston devised a system of telegraphic fire alarms, which was adopted in the city of Boston. Five so called signal circuits were extended from the city hall to different parts of the city, and in connection with these were stationed 50 signal boxes attached to buildings at convenient points. The door of each box being opened, a crank is seen with directions for the number of times it is to be turned to convey to the central office the number of the station and district. From the central station 5 wires called alarm circuits connect with the different fire bells throughout the city, the hammers of which, run by weights, are set in action by the telegraph itself and strike the number of the district and station of the alarm. The electric current is excited by a magneto-electric machine which is set in motion by the pressure of the water with which the city is supplied, and the same power is employed to wind up the weights that move the bell hammers. The bells have been rung as an experiment from Portland through the telegraph wires extending to that place, and arrangements had been made just as the Atlantic cable ceased to work to have them set in operation from the telegraphic station in London. The fire alarm also affords an incidental protection to the city from lightning. Large metallic surfaces being placed near the wires at all the stations and connected with the ground, a stroke of lightning upon the wires will leap across to these conductors, and pass harmlessly

to the ground, while the artificial current possesses too little intensity ever to overcome the intervening space, and continues in the circuit. Similar arrangements are provided upon many telegraph lines. The fire alarm telegraph is also employed to designate the exact noon by a single stroke upon the bell of the Old South church, an exact chronometer being placed in the circuit and arranged so as to pass the current at 12 o'clock precisely. By a similar arrangement in London a large ball is made to drop exactly at 12 o'clock from a pole erected in the Strand by the action of a current from the royal observatory. The same thing is also done at Nelson's monument, Edinburgh. In Paris a cannon is fired upon a similar plan. Chronometers in observatories are also made to run synchronously with a standard instrument by means of the electric current connecting them with this.-The application of the telegraph to the determination of longitude has been described in the article COAST SURVEY, vol. v. p. 397.-Upon some railroads, as the Erie road especially, the telegraph is used with great advantage for regulating the running of trains from the different stations, and it is found that a single track by its aid may safely work up to the usual capacity of two tracks.-In numerous places telegraphs have been constructed for private purposes, as from the workshops to the offices of manufacturing establishments; and for government purposes from the halls of legislation to the printing offices, thus affording the greatest facilities for the immediate printing of important public documents, and of speeches while these are in course of delivery. A system of telegraphs for the use of large cities has been recently devised by Prof. Wheatstone, by which a company will lease the use of a small wire by the year to individuals. For distances not exceeding 20 m. a copper wire no larger than a cotton thread is sufficient. Numbers of these, insulated by being wound with thread, it is proposed to bring together into one cord, and suspend as many of these as may be required from strong iron wires passed in different directions through a city upon the houses. The latter, communicating with the ground at numerous points, will convey away all atmospheric discharges that might otherwise be troublesome.-The idea of a submarine telegraph appears to have been conceived by several of the earlier electricians. Don Francisco Salva is said to have proposed one as early as 1797 between Barcelona and Palma in the island of Majorca. Experiments were made in India by Dr. O'Shaughnessy in 1839 with this object, and he insulated his wires by covering them with tarred yarn, enclosing them in split rattan, and covering this again with tarred yarn. Prof. Wheatstone in 1840 gave it as his opinion before a committee of the house of commons that a submarine communication between England and France was practicable. Prof. Morse, on Oct. 18, 1842, laid a copper wire, insulated by means of a hempen