POPULAR SCIENCE 603 



This variable hardness of flint has a distinct bearing upon the 

 characteristics of the striae imposed upon it. If a flint surface, 

 unequally patinated, be subjected to the pressure of a moving 

 point it will be seen that when this point passes over a patinated 

 area it will cut more deeply into it than when passing over one 

 of the unaltered harder portions. Thus in the passage of the 

 point over the surface of flint-scratches of varying depth and 

 appearance will be formed according to the nature of the surface 

 upon which the moving point impinges. 



It has generally been accepted as an axiom that steel will not 

 scratch flint, and if by " flint " is meant the newly broken, sound 

 variety as it is quarried from the chalk, this axiom is true. But 

 the author has found that it is possible to scratch patinated flints 

 with a steel point, and that these scratches vary in depth and 

 appearance according to the amount of patination. He also 

 found that the usual lines of shattering were produced such as 

 have already been described. 



The susceptibility of patinated flint to striation by the 

 pressure of a steel point may perhaps explain the large number 

 of scratched flints found upon the surface of the ground in cer- 

 tain localities. It seems reasonable to suppose that some of 

 these striations may have been imposed by the metal edges of 

 ploughs in their passage through the ground, the iron teeth of 

 harrows, etc., especially as it is known that such agencies can 

 produce striations of various kinds upon pieces of glass lying 

 upon the surface of the ground (figs. 9, 10). The author in this 

 article does not wish to convey the impression that he disbelieves 

 " ice-action " to have been responsible for any striations on 

 broken flints, or that these striated flint specimens have not been 

 subjected to an appreciable amount of pressure. He has tried 

 simply to show that striations may be imposed upon a flint 

 without the intervention of ice, and that it is not necessary or 

 in fact possible to invoke " enormous pressure " to account for 

 their imposition. 



The photo-micrographs accompanying this article were 

 taken by Mr. Gerald Davey of Ipswich — they are magnified 

 about nine diameters. 



