Part 9

Mr. Ronalds so far perfected his invention, that it worked accurately, though slowly, through eight miles of wire insulated in glass tubes. Having thus succeeded in putting into action his single wire telegraph, Mr. Ronalds sought the patronage of Government for its practical adoption, such a notion as that of establishing a telegraph for commercial purposes not being at that time entertained. For a length of time his application received no attention, and when at length the Lords of the Admiralty condescended to answer, they sent Mr. Ronalds, as the reward for his ingenuity, and as compensation for the time and money bestowed in perfecting the invention, the expression of their opinion--that "telegraphs are of no use in time of peace, and that during war the semaphore answered all required purposes"! This reply, so characteristic of the manner in which Government _employés_ generally regard anything new to which their attention is solicited, completely disheartened Mr. Ronalds. He abandoned the Electric Telegraph to its fate; and having gone abroad, he returned some years later to find that, notwithstanding the _dictum_ of the Lords of the Admiralty, telegraphs are of great use in time of peace as well as of war, and that the old semaphore had been entirely superseded by the means of transmission he had indicated twenty years before. Mr. Ronalds has since received a small pension, not however as a reward for his ingenious telegraph invention, but for his services in other departments of science.

The discovery of the magnetic property of an electric current by Professor Œrsted, in 1818, was most important in the subsequent progress of telegraphic invention, though it was not applied in a practical manner till nearly twenty years afterwards. In 1820, indeed, M. Ampère submitted to the Academy of Sciences at Paris a telegraphic instrument for the transmission of signals by the deflection of needles, but he adopted the impracticable plan of the earliest inventors, of having a separate wire for each letter of the alphabet. A much more important contribution to telegraphic invention by M. Ampère was the discovery of electro-magnets, which act an important part in many recent electric telegraphs.

As the magnetic properties of a voltaic current are extensively applied in electric telegraphs, it is desirable briefly to explain the nature of the action of voltaic batteries before proceeding farther with the history of the invention.

To excite a current of voltaic electricity, it is usual to employ a series of zinc and copper plates, arranged alternately in separate jars; or, what is now most common, in cells of gutta percha, separated from each other in a gutta percha trough. The cells are nearly filled with diluted sulphuric acid, and a wire is attached to each end of the trough; one being connected with the last zinc plate, and the other with the last copper plate of the opposite ends of the trough. When these wires are brought into contact, electricity is instantly generated by the action of the acid on the zinc plates. The electricity excited by the action on the zinc in one cell is carried on to the next, and that again excites and transfers an additional quantity to the third cell, thus increasing in intensity to the last pair of plates in the series. The _electric current_, as it is called, passes along the wire, and whether the wire be one yard, or whether it be a hundred miles long, the generation of electricity takes place the instant that the circuit is completed, and ends the instant that the circuit is broken. There is this difference, however, in the transmission of electricity through a long and through a short circuit, that in the former case the increased resistance offered by the length of the wire greatly diminishes the quantity of electricity transmitted though it does not perceptibly retard the velocity.

When a balanced magnetic needle is held above a short thick copper wire whilst it is transmitting an electric current, the needle is deflected from its natural position, and inclines either to the right or to the left, according to the direction in which the current passes. If, for instance, the north pole of the needle be pointed towards the copper pole of the battery, it will be deflected towards the east, but if the direction of the battery current be reversed, the deflection will be towards the west. The effect instantly ceases when the current is interrupted by breaking connection with either pole of the battery. The copper wire, though under ordinary circumstances incapable of being rendered magnetic, thus becomes endowed with strong magnetic properties when it is transmitting an electric current, and acts on the magnetic needle in the same manner as if there were an immense number of small magnets placed along the wire across its diameter.

The magnetic property of an electric current, first discovered by Œrsted, was applied by M. Ampère to impart magnetism to iron, by coiling a length of copper wire round a bar of iron, taking care to cover the wire with an insulating substance, so that when an electric current was transmitted the electricity might not pass through the iron. Coils of copper wire, covered with cotton or silk, can thus impart most powerful magnetism to a piece of soft iron; but it loses its magnetic power the instant that the electric current is interrupted.

The effect of a coil of insulated wire in increasing the magnetic power of an electric current, was applied by M. Schweigger in 1832 to increase the sensitiveness of a suspended magnetic needle. By surrounding a compass needle with several convolutions of covered wire, it was found that the deflections of the needle were much greater and more active; and he thus showed the way to the construction of those delicate galvanometers, which indicate by their deflections the slightest disturbance of electrical equilibrium. Schweigger may, therefore, be considered the original inventor of the Needle Telegraph; and as he pointed out a method of impressing symbols on paper mechanically, by means of electro-magnets, he may be considered also as the original inventor of Recording Electric Telegraphs.

The first near approach to the needle telegraph, now used in this country, was made by Baron de Schilling, who, in 1832, constructed at St. Petersburg an electric telegraph consisting of five magnetic needles. This may be considered as the precursor of the five-needle telegraph, first patented by Professor Wheatstone in 1837. By the separate deflection of those needles to the right hand or to the left, by reversing the connections with the poles of the batteries, ten primary signals could be obtained; and by bringing two into action at the same time, many more signals might be made than were required for indicating the letters of the alphabet, and they could be appropriated to express several words. For the action of this very efficient telegraph only five wires were required, and the signals being all primary ones, the messages might have been transmitted very quickly.[6] In a subsequent modification of the telegraph, he contrived to make all the signals with one magnetic needle alone, by repeating the deflections to the right and to the left, as done in the needle telegraph now generally used in England.

Another step made by Baron de Schilling was the invention of an alarum to call attention when a message was about to be sent. Some contrivance of this kind was considered essential in the early days of the practical application of the Electric Telegraph, as no one then contemplated that telegraphic communications would be so frequent as to require a person to be always near the instrument, waiting for the receipt of messages.

Baron de Schilling's alarum was very simple. One of the magnetic needles acted as a detent which held a weight suspended, and when the needle was deflected, the weight fell upon a bell. The alarums subsequently invented were constructed on the same principle, but instead of employing one of the magnetic needles as a detent, an electro-magnet was used for the purpose, and clock mechanism was introduced to sound a bell continuously, as soon as it was set in action by the withdrawal of the detent. At the present time alarums are not used in the regular stations of the electric telegraph companies; the sound of the needles, as they strike against the ivory rests on each side, being sufficient to call the attention of the clerks, who are in constant attendance.

We have hitherto been enabled to trace, step by step, the advances made at intervals--years asunder--in bringing the Electric Telegraph into practical use; but we are now approaching a time when it becomes difficult to enumerate, and impossible to describe within reasonable compass, the numerous inventions that were patented and otherwise made known for giving greater efficiency to that means of communication.

In the early part of the year 1837, the electric telegraphs of Mr. Alexander, of Edinburgh, and of Mr. Davy, were publicly exhibited in London, and excited much attention; though, at that time it was not supposed that it would be possible to make use of that means of communication for general purposes. Mr. Alexander's telegraph was the same in principle as those of M. Ampère and of Baron de Schilling, though in some respects not so efficient as either, for its action was slow, and it required a separate wire for each letter of the alphabet. It was considered a great advantage of this telegraph at the time, that it exhibited actual letters of the alphabet, instead of symbols. This was effected by having the twenty-six letters painted on a board, and concealed from view by a number of small paper screens, which were attached to magnetic needles. When any of the needles was deflected by sending an electric current through the surrounding coil, the screen was withdrawn and exposed the letter behind. Twenty-six keys, resembling those of a pianoforte, were ranged in connection, one with each wire, and on pressing down any one of the keys, contact was made between the battery and the wire connected with its associated magnetic needle; and in this manner, messages might easily be transmitted and read. The objections to this telegraph, in the form in which it was exhibited, were not only the impracticability of laying down and insulating so many wires, but the paper screens attached to the needles impeded their action, and rendered the transmission a very slow process. It is questionable, indeed, whether that telegraph could have been worked at all through a circuit of many miles.

Mr. Davy's telegraph was similar to that of Mr. Alexander's, though much more compact and better arranged. The letters were painted on ground glass, lighted behind, so that when the screens were withdrawn the letters were seen in transparency.

Professor Wheatstone, who had for some previous years been endeavouring to perfect a practical electric telegraph, took out his first patent in 1837. It closely resembled in general features the telegraph of Baron de Schilling. It consisted of five magnetic needles, ranged side by side on a horizontal line that formed the diameter of a rhomb. The needles were suspended perpendicularly, being kept in that position by having the lower ends made slightly heavier than the upper. The rhomb was divided into thirty-six equal parts by ten cross lines, and the needles were placed at the points where the lines intersected, as shown in the diagram.

At each intersection, and along the boundary lines of the rhomb, letters were marked, any one of which might be pointed at by the combined action of two of the needles. Thus, if the two extreme needles were deflected inwards, one towards the left and the other towards the right, they would point to the letter _A_ at the top of the rhomb. If the extreme needle on the left and the fourth one were similarly deflected, they would point to the letter _B_; and thus all the letters marked on the intersections of the lines could be pointed to. A telegraph that could be worked with five circuits came within the range of practicability, and it was put into operation on the Great Western Railway as far as Slough, a distance of 18 miles.

When the work of actually making communication by insulated wires between places far apart came to be done, much difficulty arose as to the best and cheapest mode of doing it. The plan first attempted was to surround the wires with pitch, and to bury them in a trench in the ground. But this was found to be attended with great inconvenience, for the pitch cracked, and electric communication was established between the adjacent wires. The method of suspending the wires on posts was, we understand, suggested by Mr. Brunel, who had seen wires so suspended for other purposes on the Continent, and he recommended it to Mr. Cooke for the Electric Telegraph. The plan was tried with success, and was generally adopted by the Electric Telegraph Company in extending their lines over the country. We shall have occasion to revert to this practical part of the subject, when describing more particularly the means of making communication from one place to another.

In continuing the history of the invention, as regards the different modes by which communications are transmitted along the insulated wires, the next telegraphs that deserve notice are those of Dr. Steinheil, which became known also in 1837. One of his telegraphs made the signals by sounds, produced by magnetic needles striking, when deflected, against bells of different tones. By another telegraph of his invention the symbols where marked upon paper by small tubes holding ink, fixed to the needles. In this manner the letters of the alphabet were indicated by dots upon a strip of paper, kept slowly moving by clock mechanism. This telegraph could be worked by a single circuit; and it appears that Dr. Steinheil was the first who discovered, or at least who practically applied, the conducting power of the earth for the return current. Each circuit, therefore, consisted of only a single wire; the wire that had been previously used to complete the circuit being superseded by burying in the earth, at each terminus, a small copper plate. Dr. Steinheil also introduced the use of galvanized iron wire. An electric telegraph of this construction was put into operation at Munich, through a distance of 12 miles.

In the following year Messrs. Cooke and Wheatstone so far simplified the arrangements of their needle telegraph as to make all the requisite signals with two needles. With a single combined battery and two wires six primary signals are thus obtained; and by repeating the deflections and combining the action of the two needles, all the letters can be readily and quickly indicated. A single needle instrument was invented by Messrs. Cooke and Wheatstone, but as there are only two primary signals, one to the right and one to the left, the deflections are necessarily repeated more frequently, and the transmission is consequently more slow. The accompanying diagram represents the alphabet of the single needle instrument. The deflections for each letter commence in the direction of the short marks, and end with the long ones. Thus, to indicate the letter _R_, the needle is first deflected once to the left and then once to the right; and the letter _D_ has the deflections reversed, beginning with one to the right and ending with one to the left. In no instance does it require more than four deflections to indicate a single letter, yet the transmission with the double needle is found so much quicker that the single needle instrument is only rarely used.

At the end of each word, it is customary for the clerk at the receiving station to indicate, by a deflection of the needle to the right, that he understands, or by a deflection to the left, that he does not understand, and in the latter case the word is repeated. In the early days of the Electric Telegraph, the transmission of 40 letters a minute with the double needle instrument was considered quick work; but the practised clerks will now transmit one hundred letters in that time, which is as fast as any person can write with pen and ink.

Since the invention of the double and single needle telegraphs there have been many modifications in the instruments, to make them work more promptly and with less vibration; but in all essential parts the telegraphs of Messrs. Cooke and Wheatstone remain unaltered, and continue to be generally used in this country.

Of the numerous other telegraph instruments that have been invented since 1837, that of Mr. Morse is in most general use, especially on the Continent and in America. Mr. Morse, indeed, claims to be the first inventor of a practical Electric Telegraph; for, according to his statement, he, in 1832, invented a telegraph, which was in principle the same as the one now in use. It was not, however, till September, 1838, that he made his instrument known in Europe, by sending a description of it with a model to the Academy of Sciences at Paris. Mr. Jackson, an American, disputed with Mr. Morse for the honour of the invention, and when the latter asserted that he had described his telegraph in 1832, to some passengers on board a packet-boat, Mr. Jackson affirmed that it was he who described it on that occasion, and that Mr. Morse, being present, got the idea from him. It is painful and difficult to decide when we find two claimants thus directly in opposition to each other, and mutually preferring charges of falsehood and fraud. The only safe guide in such cases is to refer to the earliest published and authentic descriptions of the inventions; and, following that guidance, the invention of what is called Morse's telegraph must be attributed to him whose name it bears; but we must, according to the same rule, date it several years later than 1832.

Mr. Morse's telegraph is a recording instrument, that embosses the symbols upon paper, with a point pressed down upon it by an electro-magnet. The symbols that form the alphabet consist of combinations of short and long strokes, which by their repetitions and variations, are made to stand for different letters. Thus a stroke followed by a dot signifies the letter _A_; a stroke preceded by a dot, the letter _B_; a single dot, the letter _E_; and in this manner the whole alphabet is indicated, the number of repetitions in no case exceeding four for each letter. The letters and words are distinguished from one another by a longer space being left between them than between each mark that forms only a part of a letter or of a word. The annexed diagram represents the symbols for the whole alphabet.

The mechanism of this telegraph instrument is very simple. The transmitter is merely a spring key, like that of a musical instrument, which, on being pressed down, makes contact with the voltaic battery, and sends an electric current to the receiving station. The operator at the transmitting station, by thus making contact, brings into action an electro-magnet at the station he communicates with, and that pulls down a point fixed to the soft iron lever upon a strip of paper that is kept moving by clockwork slowly under it. The duration of the pressure on the key, whether instantaneous or prolonged for a moment, occasions the difference in the lengths of the lines indented on the paper. A single circuit is sufficient for this telegraph, and a boy who is practised in the use of the instrument will transmit nearly as many words in a minute as can be sent by the double needle telegraph with two wires.

The working of Mr. Morse's telegraph, it will be observed, depends altogether upon bringing into action at the receiving station an electro-magnet of sufficient force to mechanically indent paper. Now the resistance to the passage of electricity along the wires diminishes the quantity transmitted so greatly, that at long distances it would be almost impossible to obtain sufficient power for the purpose, if it acted directly. To overcome that difficulty, an auxiliary electro-magnet is employed. The electro-magnet which is directly in connection with the telegraph wire is a small one, surrounded by about 500 yards of very fine wire, for the purpose of multiplying as much as possible the effect of the feeble current that is transmitted. The soft iron keeper, which is attracted by that magnet, is also very light, so that it may be the more readily attracted. This highly sensitive instrument serves to make and break contact with a local battery, which brings into action a large electro-magnet, and as the local battery and the magnet are close to the place where the work is to be done, any required force may be easily obtained. By this means the marks may be impressed on the paper at distances of 400 miles or more apart.

This is a very efficient and remarkably simple telegraph, and as it operates with a single wire, it has completely supplanted the needle telegraph on the Continent; though the liability to error, common to all manipulated telegraphs, is considerably increased by this mode of transmission, nor can unintelligible signals be indicated and corrected so readily as by the needle instrument.

There have been several modifications of Mr. Morse's telegraph, for the purpose of increasing the rapidity of its action and the distinctness of the marks. The most important of these was made by Mr. Bain, who in 1847 applied for this purpose the method of impressing the symbols on paper by electro-chemical decomposition. Mr. Davy had, in 1843, taken out a patent for the application of electro-chemical marks to telegraphic purposes, but his method was not sufficiently practical to be brought into use. Mr. Bain adopted an alphabet of short and long strokes, similar to that of Mr. Morse; but instead of making and breaking contact by a key pressed down by the finger, he punched holes in a strip of paper, corresponding in lengths and positions to the marks intended to be transmitted. A small metal spring, connected with the voltaic battery, pressed upon a metal cylinder attached to the telegraph wire, and when the spring and cylinder touched, an electric current was transmitted. The strip of punched paper was placed upon the cylinder so as to interrupt the circuit, excepting in the parts where the apertures allowed the spring to make contact; therefore when the strip of paper was moved along, an electric current was transmitted through the apertures, and it was stopped when the paper intervened. At the receiving station, paper well moistened with a solution of prussiate of potass and nitric acid was placed upon a corresponding cylinder to receive the message, and a piece of steel wire was kept steadily pressed upon it as it moved along. The action of the electric current at the parts where it was transmitted caused the acid to enter into combination with the steel, and the consequent deposition of iron on the paper was instantly converted by the prussiate of potass into Prussian blue. On the parts where the electric current was interrupted no action took place, and thus numbers of short and long marks were made on the paper, corresponding to the lengths of the apertures on the prepared message. A representation of the punched paper for transmitting the word "Bain" is shown in this diagram.