Faraday’s galvanometer and modern galvanometers operate on the same principle: the tendency of a magnetic element to align itself in the direction of the surrounding magnetic field. But Faraday’s instrument and modern ones function very differently. Modern galvanometers measure electric current—that is, the more or less steady rate of flow of electricity through a conductor. But Faraday’s galvanometer served primarily to measure the total quantity of electricity in a short burst of current, something that modern instruments cannot do. Faraday’s instrument possessed this distinctive electrical ability because—by mere good fortune, it seems—it boasted distinctive mechanical features that modern galvanometers do not.