In recent years considerable interest has developed'1 among chemists and physicists in the determination of the velocity of sound in liquids by means of high fre¬quency sound waves. These measurements are valuable for our knowledge of molecular properties. From a com¬parison of the velocity of sound in various homologous series, it is concluded that the spatial arrangement of the atoms in the liquid molecules plays the decisive part in the magnitude of velocity of sound. Thus aromatic compounds always have a higher velocity of sound than aliphatic compounds. Cotton and Mouton discovered that when light traverses a liquid placed in a strong magnetic field in a direction transverse to the lines of force, the liquid exhibits a feeble birefringence. The double refraction exhibited by liquids when placed in a magneto-static field is ascribed, in the theory of Langevin, to an orientation of the molecules produced by the field, the orientative couple arising from an assumed magnetic anisotropy of the molecule.