Great Facts / A Popular History and Description of the Most Remarkable Inventions During the Present Century

by Frederick C. Bakewell

This telegraph of Soemmering's, though not adapted for practical application in the form he presented it, on account of the number of wires required for the purpose, was nevertheless superior to any that had previously been invented; and by a little modification it might have been made a perfect instrument, capable of transmitting messages by means of only two wires. Such a modification of the instrument was proposed by M. Schweigger, twenty years afterwards; the only thing required being the adoption of a code of symbols, by means of which all the letters might be indicated by combinations of the four primary signals that are obtainable by two wires, as is at present done by the needle telegraph in common use. At that time, however, the discovery of the magnetic properties of the electric current, and other improvements in the means of communicating, superseded for some years the use of signals made by electro-chemical decomposition.

The next important step in the progress of telegraphic invention, after that of Mr. Soemmering, was made by Mr. Ronalds, who in 1816 succeeded in making a perfect apparatus, that transmitted every requisite signal with the use of only a single circuit. In the agent employed, however, there was a retrogression to frictional electricity and the pith-ball electrometer, for at that time the property which a voltaic current possesses of deflecting a magnetic needle had not been discovered.

Mr. Ronalds's plan was to have, at each communicating station, a good clock with a light paper disc fixed on to the seconds wheel, on which were marked all the letters of the alphabet, and the ten numerals. Only so much of this disc was exposed to view as to show a single letter at a time, through a small aperture, as the seconds wheel revolved. The clocks at the corresponding stations were set exactly together, so that the same letter was exposed to view at each instrument at the same instant. A pith-ball electrometer, connected in a single circuit with the transmitting station, was kept distended during the transmission of a message by charging the wire from an electrical machine; and when the letter required to be indicated appeared at the aperture of both instruments, the operator at the transmitting instrument instantly discharged the electricity of the wire by touching it, and thus caused the pith-balls to collapse. In this manner the person at the receiving station, by attentively watching the pith-balls, and noticing the letter that appeared at the instant of collapse, could read the messages signalled.

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.