A slight modification of a formula given by Sir W. Thomson (Phil. Mag. ii. 1871), shows that the period (t) of oscillation of a particle in a deep mass of liquid agitated by simple waves or ripples is

where λ is the wave-length, T the surface-tension, and ρ the density of the liquid. By producing, with the aid of a massive tuning-fork, steady ripples in various liquids all subjected to the same conditions, and measuring micrometrically the length of these ripples, the quantity T is determined with considerable accuracy from the above formula.