188 Correspondence—J. Reid Moir. 
the Kentian and sub-Crag implements. If a comparison is made 
oi the drawings which illustrate the Abbé Breuil’s paper, already 
mentioned, with those published by Mr. Warren, it will be seen that 
the two series portray specimens of a very similar character. Both 
papers describe and illustrate fractured flints of the haphazard 
kind, such as would be expected to be produced by some natural, 
non-human force, and it would be easily possible, by imitating 
Mr. Warren’s methods, to claim that at Belle Assise and at Grays 
there exist “‘ Natural ‘ Paleeolith’ Factories ’’, and so to emulate the 
efforts of those who, in the past, refused to believe in the human 
origin of any pre-Neolithic flaked flint. 
I notice that on p. 243 (paragraph 4) of his paper, Mr. Warren 
draws attention to one of the HKocene flints,in the following words : 
“A polished mark, associated with a series of V-shaped incipient 
fractures, indicates the passage of an intermittent jolting force... . 
Among these Bullhead flints such marks are usually lines of high 
polish, and not scratches. Upon exposure to atmospheric influences 
the crushed flint would weather out and leave a slight groove.” 
I have never yet seen a “V-shaped” incipient fracture 
such as is described above, nor do I believe that it exists, 
except in Mr. Warren’s imagination. These incipient cones of 
percussion—for that is what they are—are caused by the point of 
the agent of striation passing over the surface of the flint subjected 
to the striating movement. They are more or less circular in form, 
but, in such a case as Mr. Warren describes, none are complete, and 
a series of half-circles (occurring in a line) very close to, and some- 
times overlapping, each other is to be observed. This line indicates 
the path taken by the agent of striation, and the succession of 
contiguous semicircles is caused by the numerous blows administered 
by the unevenly travelling point of the agent of striation.! 
In course of time small cracks appear to develop from the ends of 
and extend these incipient fractures (giving rise to what are some- 
times known as “‘centipede markings”, from their superficial 
resemblance in outline to the legs of this creature), and these 
extensions have, apparently, misled Mr. Warren, and have 
induced him to describe the incipient fractures upon his specimen 
as being definitely shaped like a y. 
I am interested to see that he adopts the view, already published, 
as to the weathering out, under atmospheric influences, of such in- 
cipient fractures, but I notice that he omits to mention the original 
paper in which this matter was first made public. In case the sup- 
positions contained in this paper should turn out, eventually, to be 
* For a very complete and interesting description of analogous incipient 
fractures produced in the surface of glass by grinding and polishing the reader 
is referred to a paper entitled ‘‘ More Notes on Glass-grinding and Polishing ”’ 
by Mr. James Weir French (Transactions of the Optical Society, vol. xviii, 
January, 1917). In this paper Mr. French points out (p. 22) that the direction 
of the movement of the agent of striation was always found to be towards the 
convex side of the semicircular fractures. - 
