16 MAKKS OF I'KUCU.SSION ON SlLKIiOUS KOCKS, 



3. CONCENTRIC WRINKLES OF PERCUSSION 



(W.P.) 



PI. II., Fi^'. U. 



The vibrations of the molecviles which gave rise to the 

 cone of percussion at tlie point cf impact must necessarily 

 decrease in strength with the distance from this point. 

 Instead of a cone, curious concentric wrinkles are produced, 

 exactly like those caused by a stone throw^n into water. 

 Plate II.. Fig. i>, illustrates this feature: — 



Professor Verworn has already observed that these 

 wrinkles form an invaluable a.ssistance in determining the 

 oroximal end of an archa;olithic implement, their concavity 

 being invariably turned towards the point cf impact. This 

 is a matter of course, because the point of impact forms 

 the centre from which the vibrations radiate, and the 

 wrinkles produced on the Pollical face must naturally re- 

 present concentric circles. 



It sometimes happens that one of these wrinkles coin- 

 cidss with the line cf fracture. In that case the edge is 

 not sharp, but rounded off, and, therefore, useless for cut- 

 ling puropses. It requires sharpening by marginal chip- 

 ping (rctcuches). I have several fine specimens in my col- 

 lection, showing the partly sharpened edge, while another 

 portion still preserves its original rounded-oflF shape. Ccn- 

 sidoring that the curvature cf the wrinkles is turned to- 

 wards the Indical or External faro, it is rather difficult to 

 undeiitand why the marginal sharpening was produced by 

 blows directed from the Pollical towards the Indical face, 

 and net vice versa. v>hich seems so much easier and more 

 e.Tcctiv^. This is again rne of those problems which 

 puzzle the modern mind, and which I have frequently met 

 with in the course cf mv researches. The only explana- 

 tion I can offer is, that the archseolithic Tasmanian 

 could not possibly thhrk of any other way cf sharpening 

 'he edges than by blows directed from the Pollical face 

 ■ owards the Indical face ; it was apparently impossible for 

 him to conceive any ether methcd, and if ever he happened 

 'rJ make a mistake, he promptly corrected it by reverting 

 to the time-honoured methcd. 



4. THE SCAR OF PERCUSSION (S.P.) 



Pi. II . Fie 7. 



Frequently there appears on the Pollical face, instead 

 of either cone or wrinkles of percussion, an ellipsoidal mark. 



