In most of the uses to which rubber is put, it is subjected to deformations which are relatively small compared to the ultimate deformation of which the rubber is capable. For many products, such as vehicle tires, motor mountings, and belts, the deformations are periodic. There is, therefore, a great deal of interest attached to the physical properties of rubber when measured under vibratory, as contrasted to static, conditions. The use of rubber in mountings for the absorption or isolation of vibration, with which this paper is principally concerned, has led to a number of systematic investigations of its static properties from the standpoint of the engineer who might be interested in employing it for such purposes. As representative of such contributions may be cited the work of Keys, Smith, Brown, Haushalter, Hirshfeld and Piron, and Kimmich. The principal concern was to determine the rules which govern the deformation of rubber pieces of various sizes, shapes and hardnesses. Related questions of permanent set, creep, and the effect of temperature also came into the discussion. The importance of dynamic measurements was realized, but information on this phase of the subject was beyond the scope of the work.