passed from B to A, but when the current is interrupted, and bodies are placed between A and B, the current forces its way through them, turning and decomposing them, and producing sparks and shocks when the current passes through the human body, or any part of it. The electric force may be obtained by placing the zinc and copper discs in a pile above one another, and separating them by discs of cloth wetted with acidulated water. In this form it is called the Pile of Volta. The first application of this new power to telegraphic purposes was made by M. Som mering of Munich in 1811, and by means of a very ingenious contrivance. Upon the bottom of a glass vessel he fixed thirty-five points of gold, indicating thirty-five letters, and ten numerals from 0 to 9. From each of these thirty-five points there passed a copper conductor terminating in a small brass cylinder, in the middle of which was a groove for receiving a small screw nut for fixing the wires which united the corresponding point with the positive or negative pole of the battery or pile which he used. When the glass vessel was filled with water, and the electricity communicated to the letter at one end of a wire, the gold point coresponding to this letter gave out a bubble of gas, which was largest when it was oxygen and smallest when it was hydrogen, so that he could transmit two letters at once. Semmering covered each of his thirty-five wires with silk, and surrounded the whole with varnish. Our limits will not permit us to describe this beautiful invention more particularly, but it is obviously one capable of doing real telegraphic work, and wanted only what he added afterwards, a contrivance or alarm, for calling the attention of the operator at the distant station. Like C. M. the Bavarian mechanician never seems to have thought of reducing the number of his wires by different combinations of his gas bubbles, as afterwards suggested by Schweigger, who proposed the detonating pistol of Volta as an alarm. The grand discovery of electro-magnetism by Professor Oersted of Copenhagen, in 1819, led to great improvements in the construction and use of the electric telegraph. By placing a compass-needle parallel to the conducting wire of a Voltaic battery, that is, parallel to the current, he found that it placed itself across the current, or at right angles to the wire. When the current passed above the needle, its north pole deviated to the west, and the current came from south to north, and the same pole deviated to the east when the current came from the current passed opposite effects wer pole being deviated current passed from the west when it cam M. Ampere illustrate manner. He suppose a man to be placed in the conducting wire, the zinc pole, and the per pole, so that the the zinc to the coppe feet and came out at having its face turned needle, the effect of ways to turn its south of the figure. The thus exhibited, even w may be augmented t by the beautiful contri called a multiplier. I perceptible action upo cluded that the effect the amount of wire, an upon itself fifty or a found the result such vided none of the ele one wire to those adjac this or to insulate the of them with a silken th as to cover their surfac multipliers have been n they required a wire th long. In 1820, M. Ampere substitution of a compa tric telegraph in place o gas bubbles of Soemme ing a number of keys letter of the alphabet, other end of the twent in motion. A telegrap was actually made in Alexander in 1837, in communicated with th magnetic needles, and wrought by touching t telegraph of Sommer idea with that of Schw twenty-five wires to tv piles, we have obviously of a very high order p form telegraphic work, ble of many improver the most perfect electi present day had been th son would have thought It is to the railway syste THE ELECTRIC TELEGRAPH. 471 is country for all the advan- | account of the innumerable inventions, all aphic communication. more or less ingenious, by which telegraphic ill not permit us, nor indeed communications are generally transmitted. per place, to give an account It is difficult for ordinary readers to undercoveries of Arago and Fara- stand these operations even with the aid of agnetic properties of electric good diagrams, and those who are desirous . Arago and Ampere magnet- of making themselves master of the apparastantaneously by placing them tus commonly employed, will do this most of insulated copper wire, so satisfactorily by visiting any of the stations c current passed in a direction where an electric telegraph is placed. Our to their length. Mr. Stur- object in the present article is to give some ich applied this principle to account of the general telegraphic system, on of temporary magnets of and of the labors and services of those who merely surrounding soft iron, have been the means of introducing the elecrm of bars or of a horse shoe, tric telegraph on our railways, and who have coiled wire. The soft iron be-invented remarkable contrivances for comful magnet while the electric municating intelligence, such as the printing ng through the coil, and loses telegraph, the electro-chemical telegraph, the moment the current is stopped. autographic telegraph, and any others that Joseph Henry, now the dis- are distinguished from those commonly used etary to the Smithsonian In- by remarkable peculiarities. ced magnets which were caseveral tons, and the same been employed by Logeman - communicating permanent teel. 's beautiful discovery of elecluction in 1832, was a most in the improvement of the ph. He demonstrated by two , that an electric current is loping at a distance by inducrrents in a conducting wire. bring near to any part of a ing a closed circuit another ersed by a current, we proously on the first conductor a in a direction contrary to cing current, or that brought tor, and when we reverse the t we produce instantaneously uctor a second current movdirection as the current that r. Faraday also found that a ble of inducing similar curcting wire, and that the phetion may be produced in the e itself, an effect which is etion of a current upon itself. as thus led to the construceto-electric machine which proved by Pixii, Saxton, and ensively employed for tele 3. f notice of the history of the h, and of the principal disricity and magnetism, upon ent telegraphic apparatus is not our intention to give any We have already seen from the experiments of Sir W. Watson, and the fact was evident from every future experiment, that the electric power was transmitted along wires instantaneously, or in so short a time that its velocity could not be appreciated by the ordinary instruments by which time is measured. Any more accurate measure of its velocity was of no consequence for telegraphic purposes. Means, however, have been taken to obtain a rude estimate of its velocity, which of course must depend on the conducting power of the transmitting wire, though it does not upon its thickness. By a very ingenious apparatus Mr. Wheatstone found that the electric force moved along a copper wire at the rate of 288,000 miles in a second. According to the more recent experiments of MM. Fizeau and Gonelli its velocity is only 112,680, less than half of the preceding estimate. In the iron wire employed for telegraphic purposes, its velocity, according to MM. Fizeau and Gonelli, is only 62,000 miles in a second; according to Professor Mitchell of Cincinnati 28,500; and according to Professor Walker of the United States, 16,000 miles. But it is obvious, that whichsoever of these velocities is the correct one, the electric influence is transmitted in so short a time that an effect produced at one station is produced simultaneously with the effect produced at another. In order to transmit messages along the *The reader will find the most complete and inDr. Lardner's admirable chapter on the subject, in telligible description of telegraphic apparatus in the third and fourth volumes of his Museum of Science and Art. telegraphic wires, a certain amount of electric power is required, and this force must be increased in proportion to the length of the wire. A large wire, however, will transmit more electricity than a small one, in proportion to the squares of their diameters, or the areas of their section. According to some accurate experiments made by M. Pouillet, a distinguished member of the Institute of France, a voltaic battery of ten pairs of plates will supply electricity sufficient for telegraphic purposes by means of a copper wire one-eighth of an inch in diameter, and 600 miles in length. A force of much less intensity, however, is amply sufficient, as it is easy to strengthen the current by batteries at intermediate stations. being injured by human has observed two interes lines. In the one a dim is produced by inverse c the wires acting like a gutta percha which coa glass of the phial, the coating of the phial, and is the external coating, s electricity of the ground tralizes to a certain exten tricity of the wire. It that this disturbing cause fered with the working o wires, but the Magneto Company, who have in subterranean wire, and w messages through 500 stoppage, have not exper Having obtained a cheap and durable line for conducting the electric influence, and a simple power for generating it of sufficient in-nience from it. The oth tensity, the next step is to place the lines or served by M. Siemens is 1 wires in a proper position. The general ence upon the wires by th practice has been to support them by posts During the brilliant displ placed at the distance of sixty yards. On enon on the 18th October some lines the distance of the posts is much currents varying in intens greater; and on the great telegraphic line the line between Berlin between Turin and Genoa, the wires are car- German miles in length ried across extensive ravines and valleys, which was E.N.E. to W from half a mile to three quarters of a mile pendicular to the magnetic in width, without any support whatever, and the prevalence of this m at an enormous height above the ground. telegraphs in England we When the line reaches Turin it passes under fitted for use. ground, and when it arrives at the Maritime Alps it stretches from crest to crest, hiding itself again in the earth till it terminates at the ducal palace in Genoa. M. Siemens, whose ingenious telegraph received a Council Medal at the Great Exhibition, and which is used on all the Prussian lines, and those in the north of Germany, recommended the subterranean system of construction, and had it carried into effect on upwards of a thousand miles of German railway. By carefully covering the copper wires, which were about the 50th of an inch in diameter, with gutta percha, to prevent the escape of the electricity, by placing them about 2 feet deep in iron tubes, and by ingenious methods of discovering the locality of any defect either from the insulating coating or from the copper wire, he found the system answer so well, that at the end of three years the wires had not suffered the slightest change. There are obviously many advantages in the subterranean system. The wires are not influenced by rain or snowthey are secure against storms and hurricanes, and their locality in the earth, as well as upon the railway path, protects them from In the telegraphic li India by Dr. O'Shaughnes both the aërial and sub He found that the wires were quite insufficient in perimental line of eighty n he was obliged to employ on bamboos. Flocks of h adjutant perched upon the monkeys followed their loaded elephants broke they came in their way. thick galvanized wires s height of fourteen feet up of 200 yards apart, and system, that a soldier s from the middle of one o produced on it but a sma the subterranean system, India, Dr. O'Shaughnessy of two feet his wires, coat cha, on wooden sleepers sa nic, in order to defend the ants, which we suppose, north of Germany, recko great luxury. The wires employed fo nly made of iron about the nch in diameter. They are ating of zinc, by what is on. As zinc is very oxydonverted by the air and by oxyde of zinc, which being protects the wire from rust M. Haighton, however, has ses from the smoke of large the oxide into a sulphate, ole in water permits the wire nd to such a degree that he educed to the dimensions of g needle in less than two y peculiar conditions of the which are not galvanized, ered. On the telegraphic the extensive prairies of the graphs refuse to act in the nd August during the four e day, from 2 to 6 o'clock! contrivances, which require ke intelligible, and which rly described in Dr. Lardwe been adopted to insulate ing the posts. The wires ally pass through tubes of f glass, or they rest upon rs of the same substance. nt the bending of the wires, Interference in high winds, aced at distances of half a them, and the posts where which are larger than the led winding posts.* y stated that the electricity paratively feeble as it is, ation of the telegraph; but atmospheric electricity in of course much more injudangerous at telegraphic tural remedy for this is to on the top of each post, ly done; but at telegraphautiful and efficacious conir protection have been alker of the South-Eastern Breguet of Paris. A reper wire is placed between I the station, so that any ty imparted to the main rough the fine one before on but the effect of powon a fine wire is to fuse or to the difficulty that it has narrow a channel; so that -ar close to one of these posts ds like those of falling water tween the perforations, does not pass, and the mark, but leaves a corre this way the message of ferred in blue lines to t thousand miles off, and from the centre to the paper disc. A boy pre this record to a clerk as in ordinary type. The reader can not f the singular beauty an contrivance, imperfect a it must be. When we sa operation of perforating cording it in blue lines the wire, it seemed m any result of mechanism seen. The dry steel po spiral path, actually see blue ink upon the pap merely ingenuity that is Mr. Bain's Telegraph. quickness, and unerring it has another advant battery of much less pov of the telegraph. An e of its accuracy was rece where the importance of experienced. In an ag funds, a stock-broker from a distance an ord certain time of the day, The broker doubted th number from the magnit as the message had been ing instrument, it was f message was to purchase sols, the transcriber ha serted a cipher too many But this telegraph has which no other possess telegraph, by which indi nicate with their friends their correspondents, or their distant functionari long lines of the telegrap varied in innumerable w be impossible to deciph machine, which would d either in the possession their command in the to they reside. Any arran however, is not likely to in a small number of cas of telegraphic despatches moderate sum. But if s take place analogous to Dr. Lardner has stated, |
