598 SCIENCE PROGRESS 



natural forces. The author would like to make it clear that in 

 this article he is referring solely to the striations developed upon 

 the hard interior of the flint, and not to those observable some- 

 times upon the much softer " crust " or " cortex." 



It seems certain that to imprint a scratch upon the surface 

 of a broken flint, the more or less sharp edge of some other 

 harder material must pass over that surface under pressure. 1 

 Now there are several conditions in nature in which this simple 

 combination of circumstance might occur, and these may be 

 enumerated as follows : 



(i) In which a flint is partially embedded in the lowermost 

 stratum of a mass of ice, and dragged over portions of other 

 harder rocks forming the floor over which the ice moves (some- 

 what similar conditions would be present in the case of an ice- 

 raft with stones partially embedded in it, grounding upon a 

 shore) ; (2) in which a mass of flint gravel is resting upon some 

 resistant bed and is subjected to the pressure of moving ice, 

 which would cause some of the stones comprising the gravel to 

 be ground against each other and striations imposed upon the 

 softer specimens ; (3) in which a mass of gravel " slips " owing 

 to earth movements of various kinds or to the undermining 

 action of running water, and some of the stones in the gravel 

 are striated in the same manner and from the same immediate 

 cause as in the preceding case. It is possible also that when a 

 mass of gravel slips it may pass over some harder or softer rocks 

 (as in the case of the mass of ice mentioned) and some of the 

 flints partially embedded in its base may imprint scratches 

 upon the underlying rock or be themselves scratched as the 

 case may be. 



It has been the custom with some observers to describe 

 striations upon flints as due to what they vaguely term " ice- 

 action " and to regard parallelism of the striae as indicative of 

 such action. But as has been shown above, pressure may be 

 brought into play in geological deposits without the intervention 

 of ice, and it seems that in each case enumerated the striae pro- 

 duced might be parallel, or the reverse. 



Realising these facts the author has long ago abandoned 

 the attempt to determine whether any given flint in a geological 



1 The weathering out of spongoid and other fossils from flint surfaces some- 

 times simulates striations, but their real nature is ^generally easily discernible 

 with a lens. 



