20 MAKKS OF I'KKCUSSION ON SILICEOUS ROCKS, 



I am, unfortunately, not in the position to verify this 

 theory by experiments, which can only be carried out in a 

 laboratory well equipped for such purposes. It would, 

 however, be of the greatest interest if such experiments 

 were made, if for no other purpose than to prove or disprove 

 the view that such marks can be produced by other than 

 human agency. 



During the early part in the controversy that was 

 going on about the origin of the Eolithes, or, as I prefer to 

 call them, Archaiclithes, it has been frequently held that 

 natural agencies could produce such marks of percussion 

 av> here described, and even Prof. Verworn assumes that 

 natural processes could produce them. If a siliceous rock 

 falls from a great height on a hard surface, it is vei-y 

 probably broken if the energy developed be sufficient. If 

 the pebbles moved by the energy of a torrent strike against 

 each other, flakes may probably become detached ; even if 

 the force of the surf hurls the pebbles of the shingle against 

 hard objects it is possible that they may be broken, but 

 vv-ill all this result in tlie marks of percussion here de- 

 scribed? I certainly doubt it; never have I noticed among 

 the shingle broken pebbles showing marks of percussion, 

 nor did I notice them anywhere else. 



I maintain that any of the marks of percussion here 

 described, including those of the ineffective blows, cannot 

 be produced accidentally by natural agencies, but only by 

 the agency of a hammer held by a human hand inten- 

 tionally striking a stone. And. furthemiore. in order 

 to produce them it must be a spherically-ended hammer, 

 that is to say. a pebble, which hits the surface in one 

 j)oint only. Even if this view were considered to go too 

 far. it is absolutely certain that all specimens showing a 

 Percussion face, and on whose Pollical face the accessory 

 marks of percussion appear, must be produced by human 

 agencv, because it is impossible to assume that a boulder 

 was first divided by any kind of natural agency and after- 

 wards a similar agency acted on the plane of fracture de- 

 taching thereby a flake. 



My studies have led me to believe that, nert to the 

 Percussion face, the five accessory marks of percussion are 

 the surest signs of human agency. Retouches or rough 

 marginal chipping may be pi-oduccd by natural agencies, 

 tending to press or brcaTc off small snlinters. but the marks 

 here described can only be pi'oduced by a hammer striking 

 one point of the surface, and not penetrating into the 

 matri^t. 



