1. Orthogonal; perpendicular to a surface or to another line. 2. In the absence of an anomaly, as in a ‘‘normal time-distance curve.’’ 3. Gaussian distribution (q.v.). 4. A now-obsolete resistivity well log in which a constant current is passed between a current electrode in the sonde and a remote electrode (electrodes A and B) while the potential difference is measured between another electrode in the sonde and a reference electrode at the surface (electrodes M and N). The spacing is the distance between the A- and M-electrodes for the normal. A spacing of about 16 inches was used for the short-normal and 64 inches for the long-normal. See Figures E-10 and S-17.