FLINT FRACTURE AND FLINT IMPLEMENTS 47 



The explanation of the greater number of truncated flakes 

 upon an edge produced by fortuitous blows as compared with 

 one formed by human agency may be that in the former case 

 the rain of blows is almost continuous and the flint is continually 

 being reflaked and truncated flakes formed. It is, however, 

 somewhat difficult to imagine any human flaker being so inept 

 at his work as to be compelled to form seventeen truncated 

 flakes in the production of an edge 4% inches in length. 



The author considers therefore that the proportion of 

 truncated flakes upon a flint may furnish a further criterion 

 for the determination of human as against natural flaking. 1 

 Various other experiments in fortuitous percussion, such as 

 the hurling of a flint upon others lying on the ground, were 



F;g. 9. 



carried out, and the results found to be similar to those obtained 

 in the sack experiment. 



Experiments with Flints subjected to the Effects of Fortuitous 

 Pressure. — Experiments were conducted with an adapted letter- 

 press, and a differential screw press, with which considerable 

 pressure was obtained. 



It was found that when a suitably shaped stone was placed 

 upon the floor of the press, and another smaller stone placed on 

 the top of it and near its edge, a flake could be removed from 

 the lowermost flint by forcing the ram of the press down upon 

 the uppermost. Such flakes exhibited " opposing cones of 

 percussion " (fig. 9), due to the pressure upon the upper 

 portion of the flint being equalled by the resistance afforded 



1 In the re-sharpening of many neolithic scrapers and Moustier (palaeolithic) 

 racloirs a number of small truncated flakes were produced, but these are not of the 

 same order, or comparable to the truncated flakes described above. 



