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one great fact of his existence, and all the necessities of ease-loving mankind are subordinated to it. His labours throughout his life have been gigantic, and his ambition that of a giant rather than such as one would expect from a slim young American in the present day. But his natural insight into the powers of our world and the possibilities of our race carries him through those difficulties which to the blind and unbelieving would be impossible. Many of his inventions have a strangely doubtful value, which has made them very acceptable to the comic journalists. The New York Times suggested in 1878 that something really ought to be done to Mr. Edison, and that perhaps it had better be done with a hemp rope ; the phonograph seemed to be altogether too much for that respectable paper. The idea that your friends might keep a concealed phonograph in their drawing-room, so that when you went to call you never dare whisper how ugly and ill-furnished the room was, while you were left alone in it—that idea was bad enough; but when it came to the aerophone, then the New York Times became serious. An invention which converts whispers into is really too much;
as the Times pointed out pathetically, talk is the ruin of republics, and conversation the bane of private life. If America still wishes to preserve her great inventor, he should be requested to limit himself in the extension of man's powers to those which will add to our joys, and not to our already accumulated sorrows. Edison has unconsciously provided quite a new field for the comic sketcher : pictures of an exhausted and dying millionaire whispering his will into a phonograph ; of a lady buying so many yards of a sermon, and so many of a lecture; of a prima donna singing to the great public in the seclusion of her own sanctum ; and of safe war conferences by help of the aerophone, have made us all familiar with the funny aspect of these new powers. But with the laughter of all the comic papers in Europe ringing in our ears, we feel these things to be so grand that the ridicule is very ephemeral. These mysterious powers which lie about us, waiting for the man wise enough to find them out, are indeed aweinspiring. We cannot guess to what dimensions we are capable of growing. Already, though pigmies in actual size, we are giants upon the earth, and convert the elements into our slaves ; perhaps the future holds in its hand some power which shall enable us to break the bonds of this round globe, and speak with the far planets.
Mr. Edison's work for the science of telegraphy has been incessant and invaluable. From 1869 to 1873 Mr. Edison was engaged in a series of experiments in electric telegraphy, with a view to the improvement of the automatic telegraph by the invention of a system which should combine increase of speed with diminution of cost. The first automatic telegraph was originated by Alexander G. Bain, a Scotchman, in 1846, and the systems of subsequent inventors were developments and modifications of his, the main principle being retained in all-viz., the transmission of messages by means of telegraphic characters composed of groups of dots and dashes punched into paper. The perforated paper is introduced between two rollers connected with the wire, and a metal cylinder connected with the battery. The paper being a non-conductor, breaks the circuit between battery and line so that no electricity can pass over, but as the paper is moved forward, by hand or mechanism, the rollers and cylinder touch each other through such punctured holes in the paper as successively present themselves, and a current of electricity is transmitted along the line of wire. At the other end the current is received on a strip of paper prepared by chemicals sensitive to electricity, and the message is recorded by the decomposition of the chemicals through the action of the electricity producing marks on the paper. The three chief requisites for a perfect system of this kind are first, a mechanism for puncturing the telegraphic characters swiftly and surely at one end of the line ; second, a chemical solution appropriately sensitive to the electric current at the other end of the line; third, some method of neutralising the effects of what is known as the static discharge-a phenomenon common to all telegraph lines.
Mr. Edison set to work upon the punching apparatus, and found that the great obstacle to complete success was the difficulty of obtaining mechanism that should satisfactorily punch out the dashes; he therefore substituted for the dash an arrangement of three holes in close proximity, a larger one over two smaller ones. The electric current enters by the small dot-bole on the left, passes to the larger hole above, and thence to the small dot-hole on the right, thus making a continuous current, which records itself at the receiving end of the line as one continuous mark-in fact, a dash ; thus the letter A in telegraphic character by a dot and a dash is punched as a dot and three dots, and records itself as a dot and a line ; B, as two dots and a line, &c. The punching mechanism is connected with a keyboard, on which the operator can perform as on a musical instrument, striking each letter at will, and setting in motion the mechanism for punching it. The perforated paper is received into a box from which it is taken up by the machine. The speed averages thirty or thirty-five words a minute, but an exceptionally skilled operator attained to the speed of one hundred and ten words averaging five letters in each word.
Mr. Edison next turned his attention to the subject of the “static discharge.” He found that a message sent at an average speed over a few miles only of wire was perfectly decipherable at the other end; but if either the speed or distance were increased, the message became blurred, and on further increase was received as one continuous line. This was owing to the surplus electricity, or static current, which accumulated in the wire and prevented the current from the battery from being broken
by the intervals of non-conducting paper, and which continued after the discharge from the battery ceased. Mr. Edison arranged a magnet introduced into the circuit by means of a branch wire issuing from the main wire before it reached the receiver, and joining it again between the receiver and the earth. On reaching the branch wire the electric current parts into two, one portion passing along the main wire through the chemically-prepared receiving paper to the earth—the other following the branch wire. When this current, passing along the branch wire round the magnet, weakens in the least degree, an antagonistic current is generated by the magnet, part of which flows round the small circuit formed by the branch wire and portion of the main wire containing the receiver, while the remainder escapes to the earth. This antagonistic magnetic discharge neutralises the static discharge through the prepared paper. Another method of overcoming the effects of the static discharge is this: When the current induced by the battery ceases, the static electricity discharges itself at both ends of the wire. Consequently there is somewhere in the wire a neutral point where there is no flow. If the receiver is placed at this neutral point an incredible speed may be attained. By the use of a sufficient quantity of coiled line the neutral point may be obtained anywhere, e.g., at either end of the Atlantic cable. New York has in this manner been made the neutral point from Washington, and a speed of three thousand words a minute obtained.
The recording of the message was accomplished by means of the metal point ending the telegraph wire meeting a sheet of paper moistened with water. The current of electricity decomposes the water into its elements oxygen and hydrogen. If the metal point be of iron, the liberated oxygen attacks it, causing rust. If to the water wherewith the paper is moistened be added a chemical which combining with the rust gives a colouration to the paper, the automatic record is complete. If an iron point is used, the ferro-cyanide of potassium will unite with the particle of rust on the point and form Prussian blue. If a tin point, another chemical is used, and another colour is produced. With this enormous increase of speed to 3000 words a minute, a more sensitive solution than any hitherto used became necessary. Mr. Edison spent many months in the search for an appropriate metal and chemical, and tested many hundred working solutions. At last he hit upon the combination of the metal tellurium with paper steeped in salt water. This union produced the most perfect success. It differed from the previous combinations in that it is the hydrogen instead of the oxygen which is the active agent, forming with the tellurium a yellow compound, which quickly blackens on exposure to air. The tellurium has the additional advantage of cutting off the signals very sharply, thus aiding in overcoming the static discharge from the line. The purpose of the salt is to render the paper a better conductor, so that the water may be more rapidly decomposed.
The inventor succeeded in recording the Lord's Prayer in distinct characters in the space of an inch. To obtain a record of 3000 words a minute, each word averaging five letters, and each letter five electrical impulses, the metal and chemical must act on each other, producing a new chemical combination 45,000 times in one minute. Our speech may reach 160 words a minute. A good telegraph operator writes about forty words a minute; therefore the wire can carry as many words as twenty men can speak, talking as fast as they can, or eighty men copy in the same time. During the first year that Mr. Edison's machine was in use between New York and Washington it transmitted more than three millions of messages. Owing to litigation with rival companies, the use of it has had to be discontinued until the questions involved have been settled in the courts. During the time that the system was in practical operation the inventor was at work upon a machine which should perforate and record in the form of Roman letters, so that thus the paper might be taken direct from the wire, and delivered to the person addressed. He also conceived the idea of a small perforating machine by means of which anybody might punch his message at home and send the strip to the telegraph office for transmission. The company proposed to charge so much a yard, instead of so much a word, for the transmission, leaving the sender free to crowd as much as he liked
into the space.
Unfortunately, the litigation put a stop to the entire system, and for lack of funds these portions of the invention have never been perfected.
Another apparatus which Mr. Edison has perfected and patented is his quadruplex telegraph, by which four messages may be sent at the same time over the same wire. Two currents of diverse strength can be transmitted simultaneously in the same direction without interfering one with another, just as a ripple and a great wave may run on the same stream of water at the same time. Other two diverse currents may be transmitted in the opposite direction, and, unlike waves of water, they will meet and pass the first two without causing disturbance to any of the four. The quadruplex apparatus was used with excellent results by the Western Union Telegraph Company. The electric pen for multiplying copies of letters and drawings is another of Mr. Edison's patents, of which he owns one hundred and fifty. Of these about a dozen are of real importance; the others have been taken out rather as guards against possible infringements of the more valuable patents.
Among so many marvellous inventions, the most marvellous, at all events to the popular mind, are the varieties of speaking machines with which Mr. Edison's name is associated. It gives the impression of one's having strayed into a romance of Wonderland, instead of contemplating the solid science of a solid earth, when it comes to bottling up speech and setting it on a shelf, to be uncorked a century hence like good port wine,
or when words can be spoken into a machine, whence they shall reissue hundreds of miles away, according as may be desired, either in a great big gruff voice like that of the huge bear in the fairy-tale, or as the middle voice of the middle-sized bear, or else as the little wee soft voice of the wee-wee bear.
At the time when Professor Bell exhibited his first telephone, Mr. Edison had in his laboratory a precisely similar apparatus which he had devised some months before, for the purpose of reproducing the vibrations of a tuning-fork. Had he chanced to sound a vocal note, or utter words into this device, he would have anticipated Professor Bell in the discovery of the magneto-telephone. As it was, Professor Bell's patent, though not interfering with Edison's right to use his own machine as a reproducing apparatus for sound, debarred him from using it for the purpose of transmitting vocal effects. He therefore set to work about the invention of a galvanic transmitter. The graduated sound-waves of the human voice as received on the diaphragm of the telephone must be represented by equally graduated waves of electric current; a series of experiments was therefore entered upon with the object of determining whether any matter or compound existed, or could be formed, which would supply by its expansion and contraction a sufficiently delicate variation of resistance to produce the desired effect of increasing and decreasing the resistance of a current. He began at one end of his stock of chemicals, and tried them all—some two thousand. He found that various forms of carbon responded the best to the vibrations produced on the diaphragm of the telephone by the human voice, but none were perfectly satisfactory. He was looking round for something else to try, when his assistant brought him the broken chimney of a kerosene lamp, encrusted with lampblack from the smoke. This he scraped off, and moulded into a button about the size of a sixpence, experimented with it, and the result was a complete solution of the problem. He had now a complete telephone, independent of that of Professor Bell, and superior to his, in that the strength of the currents is not limited by the vocal power. Thus longer lines could be worked, and a greater volume of sound obtained from the receiving instrument. The carbon telephone was patented in England in 1877. But Mr. Edison's labour was only half accomplished by the perfect carbon transmitter. He next set to work upon an electro-chemical receiver. In the series of experiments already recorded in automatic telegraphy with the metal point and chemical solution, he observed this phenomenon : When a strip of paper, steeped in a solution of certain chemicals, was subjected to the action of the electric current, its surface became smoother. As soon as the current was withdrawn, it regained its normal character. If the strip of paper were placed upon a metal base connected with one pole of a volcanic battery, and a strip of platinum wire connected with the other