Adhesion
Adhesion is the mutual attraction which two bodies have for one another, as attraction between the liquid and the substance of the vessel containing it. See also Oil and Capillarity. Saunier says that the working parts in contact with each other should separate by sliding action and not by a sudden drawing asunder in a direction perpendicular to their touching surfaces, as such an action would involve the inconvenience of variable resistances, depending on the greater or less adhesion or cohesion of these surfaces. The amount of adhesion between clean surfaces is difficult to determine and it is impossible to give its exact proportion. In the case of oiled surfaces the resistance due to adhesion is proportional to the extent of the surfaces in contact.