Notes on the marks of percussion on siliceous rocks

When a solid body suffers a blow, it is obvious that that portion of the energy of the blow that is not converted into heat, must give rise to vibrations radiating from the point of impact in all directions. It is further apparent that these vibrations may not only result in detaching a flake, but if the energy was large enough, there may be a surplus, resulting in vibrations which must give rise to accessory marks, not only on the parent block, but also on the detached flake. On the other hand, the energy may not be sufficient to achieve these results, yet it must leave some traces behind at that point of the surface where the blow struck, that is to say, the point of impact. We will thus have a wide range, beginning with the inefficient blow, that is to say, a blow which was not sufficient to detach a flake, and ending with a blow of such energy not only to detach a flake, but to give rise to numerous accessory marks of percussion. Between these two extremes there must be various stages, according to the force of energy applied and the result achieved.
My studies have led me to believe that, near to the Percussion face, the five accessory marks of percussion are the surest signs of human agency. Retouches or rough marginal chipping may be produccd by natural agencies, tending to press or break off small splinters, but the marks here described can only be produced by a hammer striking one point of the surface, and not penetrating into the matrix.