Matter distributed as a thin layer between two continuous phases may fairly be said to be in a fourth state because the energy of every element is shared with those phases. This is not a distinctive character, the energy of any portion of matter in the universe is shared to a greater or less degree with every other portion by the operation of their mutual attractions. The energy of these films is, however, shared so overwhelmingly with the enveloping phases as to merit some distinctive term. The numerical value of the influence of the enveloping phases depends upon the point of reference ( see later, p. 13). One way of estimating it is by a comparison of the tensile strength of the matter in mass with its value when enclosed. C0 is the adhesion in grammes per square centimeter across an interface within the solid lubricant in mass. It was obtained in the usual way by breaking a rod. Fracture in each occurred without tangential flow. C the value when enclosed between plane faces of steel, the faces being h apart. The values in brackets were calculated from measurements made with myristic acid on the assumption that adhesion is always the same function of h