Physical properties of surfaces I - Kinetic friction

These papers describe an investigation of the physical and mechanical properties of solid surfaces, and the effect which the surfaces have on matter in their immediate vicinity. It is well known that the properties of gases, liquids and crystallizing solids are profoundly modified in the neighbourhood of a surface. There is, however, some uncertainty as to the magnitude and range of action of this surface force. Most experiments on the adsorption of gases show that the effect is confined to one or two molecular layers at the interface while in the case of liquid crystals we know that the surface effect can extend beyond this and causes an orientation of the crystal aggregates to a distance of several thousand Angstroms. Some workers have claimed that films of air or of alcoholca . 40,000 A thick apparently possessed sufficient rigidity to resist a steady pressure equal to several grammes weight. It has been shown, J however, that if the surfaces are carefully polished and are free from dust particles there is no evidence for a long range surface effect of this magnitude.