602 SCIENCE PROGRESS 



show evident signs of the usual lines of shattering in different 

 stages of weathering, and it seems that the idea that the 

 presence of deep and wide strise necessarily indicates that the 

 flint exhibiting them has been subjected to great pressure must 

 be abandoned. 



In the course of his investigations the author has noticed that 

 flints vary considerably in hardness over small portions of their 

 surface. Sometimes the specially resistant areas are readily 

 observable as their texture is quite different from the surrounding 

 material, and these may be likened to the hard " knots " which 

 occur in wood (fig. 8). But there are other and much more 

 subtle differences in hardness in the surfaces of broken flints. 

 An examination of a large series of patinated flints will show 

 that some exhibit an unequal and patchy patina, due, in the 

 author's opinion, to the varying hardness of the flint. The 

 portions of the surface which are patinated may be regarded 

 as the softer, while the unchanged areas are harder and have 

 been able to resist the patinating process. There is, however, no 

 discernible difference in the actual texture of the patinated and 

 unpatinated surfaces. Frequently a specimen is seen which 

 has been flaked at one period and patinated a certain colour. 

 Then at a later period the flint has been reflaked, arrd this new 

 flaking shows a different and less intense patina. Such speci- 

 mens are often striated and the strise on the older flaked areas 

 are of a different order to those observable on the later fracture 

 surfaces. This difference might lead some observers to think 

 that such a stone had been subjected to striation at two different 

 periods. But this may not have been the case, and the author 

 would expect the striae on the two surfaces to be different 

 owing to the difference in hardness of these surfaces, and unless 

 very definite evidence to the contrary was forthcoming would 

 prefer to favour the view that such a flint had been subjected 

 but once to the scratching process. 



The author has been able to confirm his opinion of the 

 variable hardness of flint, by subjecting examples, which to the 

 naked eye presented a perfectly homogeneous texture of surface, 

 to the action of various solvents such as dilute hydrofluoric acid 

 and carbonate of soda (heat was applied in this latter case) which 

 had the effect of simulating patination. In some cases these 

 solvents revealed resistant areas in the flint which remained un- 

 affected while the surrounding and softer portions were altered. 



