viscosity, surface tension, etc., are manifestations of the forces already known to the chemist. In all these cases the range of the forces is limited to atomic dimensions except in so far as their effects may be transmitted fromatom to atom. According to this theory, every atom in a solid or liquid is chemically combined to every adjacent atom. This chemical union may be strong or weak and may be characterized either by primary or secondary valence (Werner). In most inorganic solid or liquid substances of the strongly polar type, the identity of the molecule is wholly lost, but in organic com-pounds the groups of atoms constituting the chemical molecule usually have a real existence even in the liquid or solid state. These group molecules are held together by primary valence forces while the forces acting between the group molecules, although no less chemical than the others, are to be characterized as secondary valence forces. From this viewpoint the forces involved in adsorption and surface tension. do not originate from the group molecule as a whole, but rather from certain atoms in the molecule.