of the current is shown by the arrow. There is a migration of hydrogen atoms in the direction of the arrow through the liquid, and a migration of oxygen atoms in the opposite direction. We actually see the bubbles forming on the kathode and anode, yet we see no bubbles passing through the liquid. The formation of bubbles shows that there is actually a tearing apart of the two gases close to the surface of the electrodes, but apparently there is no such tearing apart in the body of the liquid, for we see no bubbles there.
This apparent anomaly has been cleared up on the basis of an hypothesis by Grotthus, which may be put in homely language by reference to a ball-room. Let each male dancer stand for an oxygen atom and each woman for a hydrogen atom. Let the room be crowded, and all the dancers be properly paired. A man looking down on the throng sees only couples, but no single persons. Now suppose that by some rule of the dance, at a given signal one man at one end of the room must leave his partner and cling to the wall, whilst at the same moment a woman at the other end of the room must do the same. This will disturb the homogeneity of the throng, but that can immediately be
