Electrolysis, the chemical decomposition of a substance into its constituent elements by the action of an electric current, was discovered by the English chemists Carlisle and William Nicholson (1753-1815). If an electric current is passed through water it is broken down into the two elements of which it is composed--hydrogen and oxygen. The process is used extensively in modern industry for electroplating. Michael Faraday (1791-1867) who was employed as a chemist at the Royal Institution, was responsible for introducing many of the technical terms connected with electrolysis, like electrolyte for the liquid through which the electric current is passed, and anode and cathode for the positive and negative electrodes respectively. He also established the laws of the process itself. But most people remember his name in connection with his practical demonstration of electromagnetic induction. In France Andre-Marie Ampere (1775-1836) carried out a complete mathematical study of the laws which govern the interaction between wires carrying electric currents. In Germany in 1826 a Bavarian schoolmaster Georg Ohm (1789-1854) had defined the relationship between electric pressure (voltage), current (flow rate) and resistance in a circuit (Ohm's law) but 16 years had to elapse before he received recognition for his work. Scientists were now convinced that since the flow of an electric current in a wire or a coil of wire caused it to acquire magnetic properties, the opposite might also prove to be true: a magnet could possibly be used to generate a flow of electricity. Michael Faraday had worked on this problem for ten years when finally, in 1830, he gave his famous lecture in which he demonstrated, for the first time in history, the principle of electromagnetic induction. He had constructed powerful electromagnets consisting of coils of wire. When he caused the magnetic lines of force surrounding one coil to rise and fall by interrupting or varying the flow of current, a similar current was induced in a neighbouring coil closely coupled to the first. The colossal importance of Faraday's discovery was that it paved the way for the generation of electricity by mechanical means. However, as can be seen from the drawing, the basic generator produces an alternating flow of current.(A.C.) Rotating a coil of wire steadily through a complete revolution in the steady magnetic field between the north and south poles of a magnet results in an electromotive force (E.M.F.) at its terminals which rises in value, falls back to zero, reverses in a negative direction, reaches a peak and again returns to zero. This completes one cycle or sine wave. (1Hz in S.I.units).