As originally applied by Ekman to ocean currents, a graphic representation of the way in which the theoretical wind-driven currents in the surface layers of the sea vary with depth. In an ocean which is assumed to be homogeneous, infinitely deep, unbounded and having a constant eddy viscosity, over which a uniform steady wind blows, Ekman has com¬puted that the current induced in the surface layers by the wind will have the following characteristics: (a) At the very surface the water will move at an angle of 45° cum sole from the wind direction, (b) In successively deeper layers the movement will be deflected farther and farther cum sole from the wind direction, and the speed will decrease, (c) A hodograph of the velocity vectors would form a spiral descending into the water and decreasing in amplitude exponentially with depth. The depth at which the vector first points 180° from the wind vector is called the depth of frictional influence (or depth of frictional resistance). At this depth the speed is e~* times that at the surface. The layer from the surface to the depth of frictional influence is called the layer of frictional influence. If the velocity vectors from the surface the depth of frictional influence be integrated, the resultant motion is 90° cum sole from the wind direction