Patches of sand are often found floating on the surfaces of fresh-water lakes. Most of this sand is between 0.297 mm and 0.84 mm in diameter but a few of the grains are considerably larger. Examination of the floating sand under the microscope shows that it floats because of surface tension of the water and the resistance of the sand grains to being wetted. The finer material, if of equal angularity, floats somewhat more readily than does the coarse. This may be a factor in the gradation of the sand on the lake bottom. If small waves are present the sand is picked up almost constantly and the material floats for long distances. The amount which moves out from the lake shores in this way is considerable and is probably an important factor in lake filling.