FLINT FRACTURE AND FLINT IMPLEMENTS 43 



flake removed by pressure may exhibit a well-marked cone of 

 percussion at each end. This is due to the flint having been 

 squeezed between two hard objects, and the cones represent the 

 points at which, respectively, pressure and resistance acted. 

 These cones are known as " opposing cones of percussion." 



Experiments with Flints subjected to Fortuitous Percussion. — 

 Seven or eight flint nodules of various shapes and sizes were 

 placed in a sack and violently shaken about for some little time, 

 and in such a manner that the flints were in almost continual 

 collision. It was found that only the stones of a certain shape — 

 and conforming more or less to a wedge in form (the thin edge 

 of the wedge being usually attacked) — were flaked in this process. 

 The rounded flints in the sack were not flaked, but escaped with 



Of ir-\PACT. 



Fig. 2. 



Fig. 3. 



contusion of their surfaces only. A careful examination of the 

 flaking produced by these fortuitous means, and a comparison 

 of it with that due to human blows, appears to show that there 

 is a fundamental difference between the two methods of fracture. 

 This difference is, primarily, the angles at which the flakes have 

 been removed. The method adopted to ascertain the direction 

 in which any given flake has been removed from a flint is as 

 follows : A line is drawn down the centre of the flake and at 

 right-angles to the ripple-marks (these in many cases require 

 locating with a good lens). Then two other lines are drawn 

 one on each side of the central line, and also at right-angles to 

 the ripple-marks as they curve upwards. The three lines are 

 then continued to their point of junction, which point indicates 

 the area upon which fell the blow that detached the flake (fig. 2). 1 



1 This method is adopted only when dealing with a truncated flake ; when the 

 actual bulbar cavity is present such a method is not needed. 



