1,_N0TES ^N THE MARKS OF PERCUSSION ON 

 SILICEOUS ROCKS. 



PL I. and II. 



By Fritz Noetling, M.A., Ph.D., Etc. 



(Read April 10, 1911.) 



1. INTRODUCTION. 



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, naust 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 

 & surplus, resulting in vibrations which must give rise to 

 accessoiT 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. 



It goes without further saying that the ■•-'ermanent 

 effects of ai blow must largely depend on the teinacity 

 of the substance. The more ductile it is, the larger will be 

 the energy required to detach a flake, and the more of it 

 will be spent in the pi'oduction of useless vibrations. The 

 more brittle it is, the less energy will be required, and the 

 larger is the amount of energy available for the production 

 of accessory effects. The resistance to the transmission 

 of oscillations created by the blow is another factor which 

 is of great importance. The whole jDroblem is, in fact, a 

 physical one which ought in the first instance be treated 

 on a mathematical basis, but I am afraid that it would 

 be of little use to the Archaeologist if dealt with in an ab- 

 stract sense. From his point of view it is better to study 

 ihe effects, the cause being known. 



