In geology, the total weight of airborne particles of given size, shape, and specific gravity that can be carried in one cubic mile of wind blowing at a given speed. The particles considered are only those of soil and rock (detritus). A number of measurements of sand transport by wind in the Sahara were made by Major R. A. Bagnold, who, by theory and wind tunnel experiment, established a formula depending on wind speed near the ground, diameter of the sand grains, and type of surface, but not on turbulence. For fine sand, the lower limit of effective wind is 2. 5 m s−1. A similar concept with respect to waterborne material is the sediment discharge rating. Compare competence of the wind, erosion.