THE RELATION IS DISCUSSED BETWEEN WIND FORCE AND SAND GRAINS, DEALING WITH ONE ASPECT OF A METHOD FOR COMPUTING THE NUMBER OF DAYS ON WHICH THERE IS A MOVEMENT OF SAND GRAINS ON THE GROUND. BOTH WIND DRAG AND CRITICAL WIND VELOCITY PLAY A ROLE IN THE ACCELERATION OF SAND GRAINS. THE ANGLE OF INCLINATION OF A SAND DUNE IS INVESTIGATED BY ANALOGY WITH MOTION ON AN INCLINED PLANE.