charged and to retreat when discharged, about one eighth of an inch. The lever advanced by the attraction of the magnet and was retracted by a weight or spring. The voltaic battery or generator of electricity was connected by one of its poles to one of the helices of the magnet while the other pole was connected with a mercury cup; and a conjunctive wire connected a second mercury cup to the other helix of the magnet. The circuit was closed by dipping a forked wire into the two cups of mercury, when the magnet became charged, the armature was attracted, and the lever drawn toward the magnet. When the forked wire was removed the magnet was discharged and the spring brought back the lever to its normal position. When the clock work was put in motion the ribbon of paper was drawn over the middle cylinder and the pencil attached to the lever being in constant contact with the ribbon of paper traced a continuous line lengthwise with the ribbon. in length, and directing through it a current | pencil at the bottom of the lever was thus from an electric battery. By cutting off allowed to advance when the magnet was the current, the iron becomes alternately charged and at rest with great rapidity. To form the current, it is necessary that the wire should form a circuit, or that each end of the wire should communicate with the ground. The interruption is caused by stopping this communication. The first telegraph invented by Professor Morse consisted of an electro-magnet, formed by bending a small rod of iron in the form of a horse-shoe, upon which was wound a few yards of copper wire insulated with cotton thread. This magnet was then placed upon the middle of a painter's stretching frame for canvass, the bottom of which was nailed to the edge of a common table. Across the lower part of the frame was constructed a narrow trough to hold three narrow cylinder of wood. A wooden clock was placed at one end of this trough. The cylinder next to the clock had a small pulley-wheel fixed upon its prolonged axis, outside the trough; a similar pulley-wheel was fixed upon the prolonged axis of one of the slower wheels of the train of wheels outside the clock; these two pulleywheels were connected by an endless cord or band. Upon the cylinder farthest from the clock was wound a ribbon of paper, which, when the clock train was put in motion was gradually unrolled and passing over the middle cylinder was rolled up upon the cylinder nearest the clock by means of the cord and pulleys. An A shaped pendulum was suspended by its apex from the centre of the top of the frame, directly above the centre of the middle cylinder in the trough below. This lever was made of two thin rules of wood meeting at the top but opening downwards about one inch apart and joined at the bottom by a transverse bar (which was close to the paper as it moved over the middle cylinder,) and another about one inch above it. Through the centre of these two bars a small tube was fixed through which a pencil loosely played. The pencil had a small weight upon its top to keep the point in constant contact with the paper ribbon. Upon the lever directly opposite to the poles of the electro-magnet was fastened the armature of the magnet or a small bar of soft iron. The movement of the lever was guided by stops on the frame at the sides of the lever, permitting it only a movement forward to and back from the magnet; the The pathway of the pencil point, when the lever was attracted towards and held by the magnet for a longer or shorter time, contains the three elements of points, spaces and lines, forming by their various combinations, the various conventional characters for numerals and letters. Professor Morse subsequently modified the form of his telegraph, although the principle upon which its action depended remained substantially the same. In place of the wooden cylinders operated by a wooden clock for carrying the paper band at a regular rate, he employed small brass rollers moved by means of mechanism analagous to clock-work; and instead of the armature being attached to a wooden pendulum which vibrated over the paper, he attached it to one end of a brass lever sustained in a horizontal position by two pivots, the other end of the lever being armed with a steel point. Under the soft iron armature at one end of the lever was placed an electro-magnet, while the steel point at the other end of the lever, was beneath the roller which carried the band of paper. Now when the circuit is closed-that is completed-the armature of the electromagnet is attracted through the magnetism created in the helix by the passage of the electric current, and this attraction causes the point of the pen to touch the paper and to trace upon it a line the length of which depends upon the duration of time in which the circuit remains whole. If the circuit is opened the current ceases to flow, the magnetism disappears instantly and a spring attached to the lever draws it away from the paper and the line ceases. By opening and closing the circuit rapidly dots are produced upon the paper the number of which depends upon the number of times that the circuit is broken and closed. If the circuit is closed for a longer time a dash or a short line is made upon the paper. We have thus the combinations of an alphabet of dots and lines. Thus a is a dot and a dash, b a dash and three dots, &c. The alphabet is so arranged that those letters occurring most frequently are more easily transmitted; thus e is one dot; t one dash.. An expert operator | can transmit from thirty to forty words a minute by this instrument on a land line of 200 or 300 miles in length. munication in the United States, besides the Morse, is the letter printing telegraph, invented by Mr. G. M. Phelps, and this instrument is only used in four out of the six thousand telegraphic stations in the United States. Professor Morse had no sooner shown that a telegraph could be constructed through the aid of electricity than his attention was turned to the discovery of some insulating substance by means of which the wires could be enveloped and buried in the earth, it not being deemed practicable to place them in the open air. Tarred yarn saturated with a preparation of asphaltum, was among the first insulating materials used for this purpose, and the lines constructed in 1843 were covered with this substance, and buried in the earth. This insulation proved so faulty, however, that it was at once abandoned, and the wires were insulated with glass upon poles in the open air. Still if it was decided to relinquish the idea of building subterranean lines, the fact was apparent that some good insulating material must be found which would permit the sub The transmitting apparatus is very simple, being designed only for the opening and closing of the circuit in a manner more easy than by holding the ends of the wire in the hands, as is done where there is no appara-mergence of the wires across straits or navitus. The two ends of wire are separated by two pieces of metal, one of which is a brass lever surmounted by an ivory button, and the other is a brass anvil tipped with platinum. The brass lever is mounted upon pivots, in front of the axis of which is soldered a nipple of platinum, which by the depression of the lever comes in contact with the platinum tipped anvil, and thus closes the circuit. To the Morse system at a later period, was added the "sounder," a simple contrivance, by which signals are conveyed by sound. Up to 1850 the operator read the dispatch from slips of paper to the copyist, who wrote it down. It was soon found, however, that the despatch could be read by the "click" of the instruments, and the operator now copies, himself, from sound. Several modifications of the Morse telegraph have been made, the principal of which is to substitute ink marking for embossing. The Morse telegraph in its various modifications is now used almost exclusively throughout the world. The number of inventions connected with the electric telegraph is almost endless, and would engross a long series of volumes for their description; but the only system at present in use for general telegraphic com gable rivers. Various substances were tried to accomplish this result, but nothing satisfactory was obtained until the discovery of gutta percha, which proved to be one of the most perfect insulators known, and admirably adapted by its plastic and flexible qualities for the insulation of submarine wires. In 1850 the first electric cable was laid in the open sea between England and France. This cable consisted of a solid copper wire, covered with gutta percha. The landing place in France was Cape Grissiez, from which place a few messages passed sufficient to test the accuracy of the principle. The communication thus established between the continent and England was, after a few hours, abruptly stopped. A diligent fisherman, plying his vocation, took up part of the cable in his trawl and cut off a piece which he brought in triumph to Boulogne, where he exhibited it as a specimen of rare sea-weed, with its centre filled with gold. It is believed that this piscator ignobilis returned again and again to search for further specimens of this treasure of the deep. It is, at all events, perfectly certain that he succeeded in de stroying the submarine cable. This accident caused the attention of scientific men to be directed to the discovery of some mode of preserving submarine cables from similar casualties, and it was decided, Amongst the most important submarine that the wire insulated by gutta percha lines are those which were laid across the should form a core or centre to a wire rope, Atlantic Ocean in 1865 and 1866. so as to give protection to it during the process of paying out and laying down, as well as to guard it from rocks and the anchors of vessels. The conductor of these cables consists of a copper strand of seven wires, six laid round one, and weighing 300 lbs. per mile. The insulation consists of four layers of In 1851 a cable protected in this manner gutta percha laid in alternately with four was laid between Dover and Calais, where thin layers of Chatterton's compound. g. 1 is a side elevation of the instrument, showing a section through the galvanometer coils, and Fig. 2 a cross section showing the magnetic needle. The same letters refer to like parts in both figures. A is the magnetic needle attached to the circular mirror of silvered glass a, which is suspended by a thread of cocoon silk in the brass frame B and adjusted by the screw b. The frame slides into a vertical groove in the center of the coil which divides it into two parts. The coil and mirror are enclosed in a glass case D, in order to prevent the disturbance of the needle by currents of air. The rays from the lamp E pass through the opening F, which is adjustable by the slide G, and passing through the lens M in the tube N are reflected by the mirror back through the lens upon an ivory scale at I as shown by the dotted lines. The scale is horizontal, extending to the right and left of the center of the instrument, the zero point being exactly opposite the lens. The luminous rays of light are brought to a sharp focus upon the scale by a sliding adjustment of the lens. The operator reads the signals from a point just in the rear of the magnet and coils, the light of the lamp being cut off by the screen Y so that he only sees the small luminous slit through which the light enters the instrument, and a brilliantly defined image of the slit upon the white ivory scale just above, which is kept in deep shadow by the screen Y. A very minute displacement of the magnet gives a very large movement of the ray of light on the scale I, the angular displacement of the ray of light being double that of the needle. t has ever since remained in perfect order, constituting the great channel of electrical communication between England and the continent. The success of that form of able having been thus completely estabished, lines of a similar character were subequently laid in all quarters of the world. The external protection consists of ten steel wires, each wire surrounded separately with five strands of tarred Manilla hemp and the whole laid spirally round the core, which latter is padded with tanned jute yarn. Each cable would bear eleven knots of itself in water without breaking. The deepest water encountered was 2,400 | wonderful rapidity. A low speed-some fathoms, and the distance between Valen- eight words a minute-is adopted for public tia and Hearts Content 1670 knots. The messages; but when the clerks communicate length of the cables of 1865-1896 knots; with each other, as high a speed as eighteen 1866-1858 knots. or twenty words is attained. In fact, it is said, that the only limit is the power of reading, not transmitting signals. As it is the speed of signaling is equal to, if not greater than, that attained on any land line of the same length, an achievement indicative of the skill and genius that have been directed to Atlantic telegraphy. The battery employed upon the Atlantic cables is a modification of Daniell's. 12 cells are sufficient for signaling. The receiving instrument is Thomson's Reflecting Galvanometer. This consists of a needle formed of a piece of watch spring threeeighths of an inch in length. The needle is suspended by a thread of cocoon-silk without torsion. The needle lies in the centre of an exceedingly delicate galvanometer coil. A circular mirror of silvered glass is fixed to the needle, and reflects at right angles to it in the plane of its motion. It is so curved that when the light of a lamp is thrown through a fine slit on it, the image of the slit is reflected on a scale about three feet off, placed a little above the front of the flame. Deflections to the extent of half an inch along any part of the scale are sufficient for one signal. In so delicate an instrument, the sluggish swing of the needle in finally settling into any position would destroy it susefulness. To rectify this, a strong magnet, about eight inches long, and bent concave to the instrument, is made to slide up and down a rod placed in the line of the suspending thread above the instrument. This magnet can be easily shifted as necessity may require. The oscillations of the needle due to itself are, by the aid of the strong magnet, made so sudden and short as only to broaden the spot of light. The delicacy of even this exceedingly delicate galvanometer can be immensely increased by using an astatic needle. The alphabet is made by opposite movements produced by one or other of two Morse keys. The signals need not be made from zero as a starting point. The eye can easily distinguish, at any point in the scale to which the spot of light may be deflected, the beginning and the end of a signal, and when its motion is caused by the proper action of the needle or by currents. It is thus that the mirror galvanometer is adapted to cable signaling, not only by its extreme delicacy, but also by its quickness. The deflections of the spot of light have been aptly compared to a handwriting no one letter of which is distinctly formed, but yet is quite intelligible to the practised eye. Signals in this way follow each other with Telegraphic stations must be united by one insulated wire, either carried overland, or under the sea. The insulation of land lines is insured by attaching the wires to insulators fixed on posts some twenty feet high. The posts are placed at distances of about sixty yards apart. Insulators are of all shapes and many materials. The insulator most generally used in the United States is made of glass, and is supported by a wooden pin. The leakage in a long line, notwithstanding the best insulation, is considerable. The loss at each post is insignificant, but when hundreds or thousands are taken into account it becomes decided; so that in extremely wet weather in some cases merely a fraction of the total current that sets out reaches the earth at the distant station. The wire most employed for land lines in the United States is No. 9 galvanized iron wire, although there is considerable of No. 8, and a few thousand miles of No. 7 and 6 in use. But a little more than a quarter of a century has elapsed since the electric telegraph was introduced to the public as a practical means of communicating intelligence. The first line constructed in the United States was put in operation in the month of June, 1844, between Washington and Baltimore. Up to this time the electric telegraph had been regarded only as a curious theoretical science without practical application. As far back as 1834, Messrs. Gauss and Weber constructed a line of telegraph over the houses and steeples of Gottingen, using galvanic electricity and the phenomenon of magnetic induction as a motor. The slow oscillations of magnetic bars, caused by the passage of electric currents, and observed through a telescope furnished the signals for corresponding, but the operation was complicated, slow and inefficient. In 1837, M. Steinheil established a line of telegraph be tween Munich and Bogenhausen, a distance | make them a present of a hundred dollars, of twelve miles; and in 1838, Professor but that he would not have his name assoWheatstone constructed a line between ciated as a stockholder in so wild and chimeLondon and Birmingham, but the apparatus rical a scheme. After the line was comemployed by each was crude and unsatisfac-pleted, this incorrigible skeptic was amongst tory, and it was not until Professor Morse the first and best patrons of the company. perfected his simple and reliable system, As a natural consequence of the distrust that the electric telegraph became of practi- of capitalists, and the great difficulty of raiscal utility. ing funds for properly building the lines, |