LONDON. Royal Society, December 3.—Sir William Crookes, president, in the chair.—M. de Lange: The thermophone—a new form of telephone.—Dr. G. S. Walpole: Hermann's phenomenon. At the boundary between two solutions of unequal specific conductivity a change reaction is developed if a difference of potential be maintained between them. Alkali is liberated if the current passes from the better conducting solution to that not conducting so well; acid, if the current passes in the opposite direction. The amounts may be calculated from the potential gradients in the solutions on each side of the boundary, the time for which the difference of potential is maintained, the resistance constant of the vessel employed, the dissociation constant of water, and the known migration velocities of hydrogen and hydroxyl ions.