Soon after having invented his telegraph, he came over to London, and spent the rest of the year in making a variety of instruments, and in efforts to get his telegraph introduced on the Liverpool and Manchester Railway. He found an obstacle to the complete success of his mechanical telegraph, in the difficulty of transmitting to a distance sufficient electric power to work the electro magnet upon which its action depended. A friend advised him to consult Professor Wheatstone, then known to be deeply engaged in electrical experiments, with a view to telegraphy; and accordingly, an interview between them took place in February 1837. II.--PROFESSOR WHEATSTONE. 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