A graphic record of the measured or computed physical characteristics of the rock section encountered in a well, plotted as a continuous function of depth. Measurements are made by a sonde as it is withdrawn from the borehole by a wire line. Several measurements are usually made simultaneously, and the resulting curves are displayed side by side on a common depth scale. Both the full display and the individual curves are called logs. Well logs are commonly referred to by generic type, such as resistivity log and radioactivity log, or by specific curve type, such as sonic log and gamma-ray log.