Comparative measurements of the clay fraction of soils were made with a beta‐ray gauge system, a density meter, and a hydrometer. Reliable clay fraction determinations could be made by a beta‐ray gauge, and a density meter in less than 25 minutes of sedimentation. The beta‐ray gauge measured clay fractions were not affected by surface tension which was the possible cause for variable results obtained with the gamma‐ray attenuation technique.