136 The Palwolithic Implements and Gravels of Knowle, Wilts. 
flint-gravels, would be sufticient to account for scratches in every 
direction, quite definite, and well defined. Such a statement is 
not easy to disprove, but we feel very doubtful whether a mere 
land-slip would be likely to produce scratching on such a hard 
substance as flint. Although unable to prove definitely that such 
earth movements could not effect the scratching of flint, the im- 
probability of this has been emphasised by certain rough experi- 
ments recently undertaken, in which we have tried artificially to 
scratch flint with flint, and have been impressed by the difficulty 
of producing even obscure and indistinct seratchings. 
A further suggestion is that river action might produce scratches 
of this nature upon flints. That is to say, that in the rubbing 
together in a river bed such scratches might be produced. It is 
difficult to conceive that the bouldering action of a river bed could 
produce scratches, recognisable as such, and indeed, if this be the 
case, we may ask why do not flints from a// river gravels exhibit 
similar markings ? 
Still another theory advanced, is that the marks in question are 
in reality cracks produced by blows, and not scratches at all. 
Certainly the flints in a bed of gravel will have undergone a good 
deal of knocking together, but while occasional cracks might be 
produced, there does not seem to be sufficient reason for regarding 
the marks as principally due to such a cause. The crucial test, 
also, of examining a marked flint which has been broken in two, 
points clearly in the same direction, for generally speaking no 
trace of cracks extending from the surface is revealed. 
We come back, then, to the much-vexed question of the glacial 
scratching of flint. It is by no means at variance with the 
geological record, to suppose that certain constituents of these 
gravels have been subjected to glacial action. The great ice sheet 
of Northern Europe is generally considered to have reached down 
to a point not very far north of Knowle, and it is not unreasonable 
to suppose that subsidiary smaller glaciers may have extended still 
further south, under the influence of the extreme cold. Lord 
Avebury! has pointed out the evidence of glacial action that the 
1“ The Scenery of England.” 

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