The influence of the wind laden with sand in modelling pebbles is believed by some authors to be only that of polishing the surface, by others of rounding off bits of stone that already possessed edges and corners, or again by others of wearing any fragment either rounded or angular into definite forms with ridges and facets, dependent on the shape of the basis (Alb. Heim). Experiments, fully confirming the last opinion, are described in this paper: no rounding off took place, while the models were slowly revolved in the sandblast, and vertical planes took on a backward slanting position, cutting eachother along sharp edges. Where sand corrosion is great, as in the desert, the windworn pebbles owe their shape to the laws formulated by Heim; many of the fossil windworn pebbles of Northern Europe have undergone but slight alteration from their original shape and size by the natural sandblast, others seem to have been entirely remodelled by the wind along the lines indicated above.