A very pretty method of regulating clocks by a standard clock is that in use at Edinburgh. On the pendulum rod of the clock to be regulated, and low down on the same, is a coil of fine covered wire wound round a short tube. Two permanent magnets are placed in line with each other, with their N or S ends close together and the other ends attached to the clock-case, in such a manner that the coil, on swinging with the pendulum, can slide over the magnets without touching. The terminal wires of the coil are led up to near the point of suspension of the pendulum, so as not to affect its swing, and the regulating current is sent through a wire like a telegraph wire from the standard clock, and from this wire round the coil and then to the earth, or back by another wire. Currents are sent through the wires in contrary directions during each successive second, so that the current in the coil flows in one direction during its swing from, say, right to left, and in the contrary direction when swinging from left to right; the effect of the current flowing in one direction is to cause one magnet to repel the coil off it, and the other to attract it over it, so that there is a tendency to throw the coil from one side of its swing to the other, and back again when the current is reversed. A little consideration will make it clear that if the pendulum tries to go too fast the coil will tend to commence its return swing before the current assisting the previous swing has stopped, and it will therefore meet with resistance, and be brought back to correct time.