In order to interpolate between thermometrically determined depths of sampling in serial oceanographic observations it ha.s been customary to plot a curve of depth to wire length ratio against wire length. It is shown that a simpler and probably more accurate method consists of plotting wire length minus depth against wire length. In this method the surface wire angle is converted into a line of tangency to the curve which always terminates at the zero point of the graph. Furthermore, the limiting slope of this curve is more readily defined and utilized.