BY FKITZ NOETLINd, M.A., PH.D., ETC. 15- 



I cannot find any reference to this peculiar effect of per- 

 cussion, but it is unquestionable that it represents nothing 

 but the top of an abortive cone of percussion. 



Professor Verworn mentions certain featiires which he 

 calls "conical fissvu-es " occurring on the percussion face. 

 These conical fissures turn their convexity towards the 

 indical face, while the convexity of the process of percus- 

 sion is directed towards the pollical face. 



There is no doubt that both features are closely con- 

 nected, probably re23resenting a more or less imperfect cone 

 of percussion. 



I never observed conical fissures in the Tasmanian 

 tero-watta, while it seems that the process of percussion haa 

 not been observed in European archseolithes. This may 

 probably be due to the difference in the nature of horn- 

 stone and flint, though it requires further obesrvatious be- 

 fore this view can be considered as certain. 



2. THE CONE OR BULB OF PERCUSSION (C.P.) 

 PI. II., Fijr. 6. 



Perhaps the most characterisitc feature is the cone, or,, 

 as it is frequently called, the bulb of percussion (1). It is 

 always situated at the proximal end of the Pollical face, 

 and its point merges into the Percussion face. (Plate II., 

 Fig. () ) 



The occnrrence of this cone in the Tasmaniaji tero-watta 

 is rather peculiar. In the first instance, it represents 

 always a truncated cone, the point being cut oflF by the 

 Percussion face; secondly, it is always composite, being com- 

 posed of several cones showing difforent angles of sides, 

 the top portion showing invariably a more acute angle than 

 lower portion. Generally two cones, separated by a sharp 

 edge, are formed. The top or proximal cone showing au. 

 angle of about SOdeg., the lower, or distal cone, having an 

 angle of about 60deg. In rarer instances the lower por- 

 tion IS composed of two cones, whose angles, however, differ 

 very little. So far I never observed that the top cone \vas 

 divided into two portions. 



Sir John Evans has given a very ingenious explanation 

 of the origin of the cone of percussion. The only question 

 wo mipht ask is. how is it, that if this purely m8cha.nical ex- 

 planation be correct, that the cone of percussion is only 

 produced in siliceous rocks and minerals ? 



(1) The term bulb of percussion was acconliiis to .Sir Jolin Evan.s first used 

 by the late Dr. Hugh Falcmer. 



