Of all the marvels of our time, the most marvellous is the subjugation of the electric fluid, that potent elemental force,—twin brother of the fatal lightning,—to be our submissive courier, to bear our messages from land to land, and "put a girdle round about the earth in forty minutes." The Prospero that tamed this Ariel was no individual genius, but "two single gentlemen rolled into one." The idea of employing the electric current for the conveyance of signals between distant points, can be traced pretty far back in date; but to Mr. Cooke and Professor Wheatstone is undoubtedly due the credit of having made the electric telegraph an actual and accomplished fact, and rendered it practicable for everyday uses.

Having served for a number of years as an officer in our Indian army, Mr. Cooke came back to Europe to recruit his health in the beginning of 1836, and took up his abode at Heidelberg. He found agreeable occupation for his leisure in the study of anatomy, and in the construction of anatomical models for his father's museum at Durham, where he was a professor in the university. Entirely self-taught in this delicate art, Mr. Cooke applied himself to it with characteristic ardour, and attained remarkable skill. One day he happened to witness some experiments which were made by Professor MÖncke, to illustrate the feasibility of electric signalling. A current of electricity was passed through a long wire, and set a magnetic needle at the end quivering under its influence. The experiment was a very simple one, and not at all novel; but Cooke had never paid any attention to the subject before, and was much struck with what he saw. He became strongly impressed with the possibility of employing electricity in the transmission of telegraphic intelligence between distant places. From the day he witnessed the experiments in Professor MÖncke's classroom, he forsook the dissecting knife, threw aside his modelling tools, and applied himself to the realization of his conception. With such ardour and devotion did he labour, and such skill and ingenuity did he bring to the work, that within three weeks he had constructed a telegraph with six wires, forming three complete metallic currents, and influencing three needles, by the varied inclination of which twenty-six different signals were designated. In that short time he had also invented the detector, by which injuries to the wires, whether from water, fracture, or contact with substances capable of diverting the current, were readily traced, and the alarum, by which notice is given at one end of the wire that a message is coming from the other. Both these contrivances were of the utmost value,—indeed, without them electric telegraphy would be impracticable,—and are still in use. Possessing more of a mechanical than a scientific genius, Mr. Cooke bestowed more of his time and ingenuity on the perfection of a telegraph to be worked by clock mechanism, set in action by the withdrawal of a detent by an electro magnet than in the completion of the electric telegraph pure and simple.

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.