238 A XATURAL 'EOLITH ' FACTORY/, [vol. lxxvi. 



7. A Natural 'Eolith' Factory beneath the Thaket Sand. 

 By Samuel Hazzledi> t e Warrex, F.Gr.S. (Eead May 5th, 



1920.) 



[Plate XV.] 



Experiment lias shown that the mechanical increment of one 

 flint grinding against another under pressure will produce edge- 

 chipping similar in every respect to that which is seen upon the 

 Eoliths. 



Direct evidences that such processes have actually heen in opera- 

 tion in Nature have been brought forward by M. i'Abbe H. Breuil l 

 and Mr. F. N. Ha ward, 3 as also by the present writer 3 ; but more 

 comprehensive knowledge of the work of Nature is urgently 

 needed. 



One must never forget that static energy in equilibrium is in- 

 effective : there must be some disturbance of equilibrium for any 

 chipping force to be set in action. That is to say, there must be 

 at least vibration, but the greater the differential movements, and 

 as a consequence the more the stones grind over each other, the 

 more favourable the conditions become for the production of edge- 

 chipping. 



Certain types of superficial drift fulfil these conditions, through 

 the prolonged operations of soil-creep, better than they can be 

 fulfilled in more deeply seated situations. But the Eoliths that 

 are found in them, which some investigators believe to be results 

 of these mechanical movements, can always be claimed by others 

 as human implements. 



The conditions at the base of the Tertiary System do not always 

 fulfil what is needed. The section at Harefield can be taken 

 as a good illustration : here is evidence of immense pressure, 

 without any appreciable amount of differential movement. In 

 consequence Ave find that the fractures are promiscuous, and strike 

 through the heart of the flints in any direction, and there is a 

 general absence of that type of edge-chipping which is produced 

 when the flints grind over each other. 



In the Bullhead Bed, exposed in the big chalk-pit to the west 

 of the Stifford road at Grays in Essex, the conditions are much 

 more favourable. The great development of slickensides gives 

 sufficient testimony to the differential movements which have taken 

 place. 



The accompanying diagrammatic section will make the relation 

 of the deposits clear. At the top is the contorted Trail, usually 



1 ' Sur la Presence d'Eolithes a la Base de l'Eocene Parisien ' L' Anthro- 

 pologic, vol. xxi (1910) p. 382. 



2 Proc. Prehist. Soc. E. Anglia, vol. i (1912) p. 185 ; ibid. (1913) p. 347 ; 

 and vol. iii (1919) p. 118. 



3 Journ. R. Anthrop. Inst. vol. xliv (1914) p. 431. 



