462 



NATURE 



[December 26, 1912 



were evidently detached by blows delivered on the 

 side of Ihc edge. 



When Making flints I find that it is only this type 

 of blow which will produce a sharp cutting edge ; I 

 conclude that these were flaked for that purpose, and 

 consequently that they have been fabricated by man 

 for some cutting or scraping purpose. 



(3) The fortuitous flakes also nearly always show 

 on their surfaces prominent undulations or ripple 

 marks, caused by the fact that they were detached by 

 blows which struck tlie edge obliquely (Fig. i). 



As there are iSo angles at which a flake can be 

 removed from the edge of a flint, and as it is only 

 ■ the higher angles which will remove flakes showing 

 no ripple-marks, it is seen that nature has many 

 more chances of delivering oblique blows which detach 

 flakes showing this peculiarity. Observations have 

 shown that as the obliquit}' of tlie blow increases or 

 decreases, the visibility of the ripple-marks increases 



or decreases. It has been found that to detach a flake 

 obliquely is a very difficult task, and that generally 

 in doing so several blows have to be delivered which 

 have the eflect of shattering and blunting the edge 

 which is being produced. 



It is, however, a very easy matter to detach flakes 

 by vertical blows (Fig. 2), and, moreover, by so doing 

 an excellent sharp edge is formed. As the flaked 

 flints I find have been flalced by vertical blows, I 

 conclude that man has been the fracturing agent. 



(4) It was also noticed tliat the fortuitous flakes 

 had been removed by blows falling at different angles 

 to the edge of the stone (Fig. 3). 



The method I adopt to arrive at the angle at which 

 (lie blow fell which detached any particular flake, if 

 I 111- actual bulbar cavity is not visible, is to draw a 

 line down the centre of tlie flake and at right angles 

 to the ripple-marks, and then to draw two others on 

 each side of and equidistant from the centre one, and 



NO. 2252, VOL. go] 



also at right angles to the ripple-marks as they curve- 

 upwards (l^ig. 4j. 



These three lines must then be continued out unil 

 they meet, and the point of juncture will be found to 

 be the spot where the blow fell wliich detached the 

 flake. The other method is to examine the surface 

 of the flake for those small fissures which result from 

 a blow and "fan out" from the point of impact 

 (Fig. 5)- 



Tlie flints considered to be "human " show that the 

 flakes have been removed at a constant angle to the 

 edge of tlie flint, and by flaking stones I find that 

 this must of necessity be so (Fig. b). To try to put an 

 edge on a flint by blows delivered at different angles 

 would be a very troublesome and useless procedure. 

 I also found that the flaked edges of the flints pro- 

 duced in my sack experiment showed a large number 

 of truncated flakes. On one specimen I counted 

 seventeen on one edge 45 in. long. These truncated 

 flakes are those which Iiave got 

 diminished in size or cut off by the later 

 flaking of the edge (Fig. 7). 



In my sack experiment, where the 

 rain of blows is practically continuous, 

 the edge of the flint is continually being 

 re-flaked, and in consequence truncated 

 flakes are formed. On the other hand, 

 the stones I look upon as having been 

 humanly struck do not show many 

 truncated flakes, and, as when flaking 

 flints myself I find it is not necessary 

 to make many such flakes in forming 

 a cutting edge, I conclude that man 

 has been the fracturing agent in the 

 case of these specimens. 



In nearly every flint which I havt^ 

 flaked by fortuitous blows I find thai 

 a distinct sinuous edge, similar to that 

 seen upon many Palaeolithic and Neo- 

 lithic implements, is produced, and at 

 first sight might lead to the conclusion 

 that nature can exactly imitate man's 

 worlc, but an examination of the details 

 of the individual flal-ces, such as I have 

 outlined above, at once shows that this 

 is not so. 



I will now give the results of my 

 experiments with flints under pressure. 

 (i) I find that when a flint is placed 

 upon the hard floor of the press, and 

 a large amount of pressure exerted 

 upon it with the ram, it will break in 

 half, and that the broken surface ex- 

 hibits two bulbs, at each point where 

 pressure and resistance acted (Fig. 8). 

 The bulb which is formed on the side of the flint 

 resting on the floor of the press is always more pro- 

 minent and better formed than that at the opposite 

 side, where the ram impinged. I am, however, unable 

 at present to say why this should be so. None of the 

 flaked flints found in the pre-river-drift deposits show 

 these two bulbs, and I therefore conclude that man 

 has produced them, because it is impossible to form- 

 two such bulbs on one flake by detaching it with a 

 blow. 



(2) It w'as found that if a folded duster or piece of 

 cloth was placed upon the floor of the press, thus 

 giving the flint a soft base upon which to rest, 

 with greater pressure than was needed in the former 

 case, a flake was detached showing only one bulb. 

 This bulb, however, is of a different character from one 

 produced by a blow, being flat and only partly de- 

 veloped, and as I do not find such bulbs on the flints 

 we look upon as "human," I conclude that man ' 



