600 SCIENCE PROGRESS 



bination of both these characteristics (fig. 2), and the author 

 concluded therefore that when these flints were first attacked 

 by the agent of striation a line of shattering was in nearly every 

 case produced and that the shattered portion of flint was gradu- 

 ally removed by some natural process (fig. 3). It seems clear 

 that continued exposure to the effects of damp and changes of 

 temperature would be quite competent to remove these thin 

 minute plates of flint, and that it might be held therefore that 

 the well-marked grooves represented simply " weathered-out " 

 lines of shattering. The next point to clear up was the amount 

 of pressure needed to produce lines of shattering upon a flint 

 surface, and a series of specimens was collected composed of 

 newly broken sound flint fresh from the chalk, and of others 

 from various sites which exhibited different degrees of " patina- 

 tion " or surface change. The author then procured a piece of 

 sound flint from the chalk, and having broken it in such a manner 

 that a sharp edge was produced, commenced to attempt to 

 impose lines of shattering with it, upon the various specimens 

 mentioned, by utilising the strength available in his right arm. 

 These experiments demonstrated that while it was impossible 

 to scratch the newly broken, sound flint, the other specimens 

 could be scratched, and that the visibility of the markings 

 produced increased with the degree of patination of the speci- 

 mens. It was noticed also that nearly all the flints so scratched 

 exhibited similar lines of shattering (composed of thin minute 

 plates of flint) to those observable upon the specimens striated 

 under natural conditions. 



The exact cause of the patination of flint is at present obscure 

 (it is possible that several causes may be able to produce it), 

 but it generally shows itself in a distinct colour change of the 

 surface. There appear to be three distinct stages of patination. 

 The first is when the flint is attacked slightly and exhibits a light 

 blue coloration due to the black interior showing through the 

 thin white film spread over it. The second is represented by 

 a denser blue, and the third by pure white which indicates that 

 the patina is thick enough to obliterate the black background 

 on which it has formed. 1 There is another condition sometimes 

 present in flint which may be related to patination, in which 

 the specimen does not exhibit any colour change, but has a 



1 The phenomenon of the staining of flint by various substances is quite a 

 separate phenomenon to patination, and has no bearing on the present inquiry. 



