After making a careful study of the Great Salt Lake oolites, the author concludes that the oolites of the zonal type originate at the water's edge, are washed upon the mud flats, and grow as they are driven inland by the wind. The laminae correspond to the seasonal changes of the area, and are the result of direct precipitation of amorphous aragonite from the evaporation of capillary water. The growth occurs during the early summer months when the temperature rise is greatest.