Mr. Charles Wheatstone, F.R.S., and Professor of Experimental Philosophy in King's College at the time of that interview, had made considerable advances in the scientific part of the enterprise. At the commencement of his career as a maker and seller of musical instruments in London, he was led to investigate the science of sound; and from his researches in that direction, he was led—much as Herschel was led—to devote himself to optics, and to study the philosophy of light. He was the first to point out the peculiarity of binocular vision, and to describe the stereoscope, which has since become so popular an instrument. Gradually, however, his thoughts and researches came to be steadfastly directed to the application of electricity to the communication of signals. In determining the rate at which the electric current travels through a wire he had laid down, he made an important stride towards the end in view. He proved by a series of most ingenious experiments, that one spark of electricity leaps on before another, and that its progress is a question of time. He found that electricity travels through a copper wire as fast as, if not faster, than light, that is, at the rate of 200,000 miles in a second; but through an iron wire, electricity moves at the rate of only 15,400 miles in a second. In 1836 Mr. Wheatstone had begun experiments in the vaults of King's College, with four miles of wire, properly insulated, and was working out the details of a telegraph, the scientific principles of which he had already laid down. He had discovered an original method of converting a few wires into a considerable number of circuits, so that the greatest number of signals could be transmitted by a limited number of wires, by the deflection of magnetic needles. Mr. Wheatstone, however, was somewhat backward in the mechanical parts of the scheme, and the meeting between him and Cooke was therefore of the greatest benefit to both, and an admirable illustration of the old proverb, that two heads are better than one. Had they never been brought together,—had they kept on working out their own ideas apart—each would, no doubt, have been able to produce an electric telegraph; but a great deal of time would have been lost, and their respective efforts less complete and valuable than the one they effected in conjunction. Cooke wanted sound, scientific knowledge; Wheatstone wanted mechanical ingenuity; and their union supplied mutual deficiencies. A partnership was immediately formed between them. Before their combined genius all difficulties vanished; and in the June of the same year they were able to take out a patent for a telegraph with five wires and five needles. Their respective shares in its invention are clearly marked out by Sir J. Brunel and Professor Daniell, who, as arbiters between the two upon that delicate question, gave the following award in 1841:—

"Whilst Mr. Cooke is entitled to stand alone as the gentleman to whom this country is indebted for having practically introduced and carried out the electric telegraph as a useful undertaking, promising to be a work of national importance; and Professor Wheatstone is acknowledged as the scientific man whose profound and successful researches had already prepared the public to receive it as a project capable of practical application,—it is to the united labours of two gentlemen so well qualified for mutual assistance, that we must attribute the rapid progress which this important invention has made during the five years since they have been associated."

Shortly after the taking out of a patent, wires were laid down between Euston Square Terminus and Camden Town Station, on the North-Western Railway; and the new telegraph was subjected to trial. Late in the evening of the 25th July 1837, in a dingy little room in one of the Euston Square offices, Professor Wheatstone sat alone, with a hand on each handle of the signal instrument, and an anxious eye upon the dial, with its needles as yet in motionless repose. In another little room at the Camden Town Station, Mr. Cooke was seated in a similar position before the instrument at the other end of the wires, along with Mr., now Sir Charles Fox, Robert Stephenson, and some other gentlemen. It was a trying, agitating moment for the two inventors,—how Wheatstone's pulse must have throbbed, and his heart beat, as he jerked the handle, broke the electric current, and sent the needles quivering on the dial; in what suspense he must have spent the next few minutes, holding his breath as though to hear his fellow's voice, and almost afraid to look at the dial lest no answer should be made; with what a thrill of joy must each have seen the needles wag knowingly and spell out their precious message,—the "All's well; thank God," that flashed from heart to heart, along the line of senseless wire. "Never," said Wheatstone, "did I feel such a tumultuous sensation before, as when all alone in the still room I heard the needles click; and as I spelled the words, I felt all the magnitude of the invention now proved to be practicable beyond cavil or dispute."

A few days before this trial of the telegraph in London, Steinheil, of Munich, is said to have had one of his own invention at work there; and it is a difficult question to decide whether he or Cooke and Wheatstone were the first inventors. It is, however, a question of no consequence, as each worked independently. Since the first English electric telegraph was patented, there have been a thousand and one other contrivances of a similar kind taken out; but it may be doubted whether, for practical purposes, the original apparatus, with the improvements which its own inventors have made on it, is not still the best of them all.

From being used merely to carry railway messages, the telegraph was brought into the service of the general public; the advantages of such almost instantaneous communication were readily appreciated; and eight years after Messrs. Cooke and Wheatstone took out their patent, lines of telegraph to the extent of 500 miles were in operation in England upon the original plan. In 1855 telegraphic correspondence had become so general, that the Electric Telegraph Company was started to supply the demand. In that establishment the Needle Telegraph of Wheatstone and Cooke is the one generally used, with the Chemical Recording Telegraph of Bain for special occasions. By means of the latter, blue lines of various lengths, according to an alphabet, are drawn upon a ribbon of paper, and as many as 20,000 words can be sent in an hour, though the ordinary rate is 100 per minute. In the purchase of patent rights alone, the Company have spent £170,000, and they are every year adding to the length of their wires. In June 1850 they had 6730 miles of wires, and despatched 29,245 messages a year. In December 1853 they had 24,340 miles of wires, and despatched 212,440 messages a-year. Their lines now extend over a much larger mileage, and convey a greatly increased number of messages. The Magnetic Telegraph Company have also a large extent of wires, and do a considerable business.