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of it may be found adhering to the surface of the flints, and even 
to the surfaces which have been worked by man. In certain 
instances, where a stone appears to have split during working, the 
dioxide has penetrated into the cracks and effectively recemented 
it! We have also observed deposits of manganese dioxide on the 
_sarsen fragments found in the gravel at Knowle. 
We have yet to refer to the secondary deposits of silica which 
are not infrequently found on the surface of the flints. It is not 
easy to understand what were the chemical and physical conditions 
which prevailed when these deposits took place, but there can be 
no doubt as to their frequent occurrence. The silica is generally 
_ of the chalcedonic variety, occasionally assuming a fibrous structure, 
-—moss-like or in small rods. Such deposits of silica do not usually 
‘present a polished surface. The layers are generally very thin, 
and are frequently much worn down, sometimes only a mere film 
remaining. Very distinct patches of the botryoidal form may 
occasionally be found even on the worked surfaces of implements 
from this, as well as from other localities, though the fact appears 
to have been very generally overlooked. Some well-defined im- 
-plements closely covered with scratches, appear to have received a 
thick deposit of white silica which has filled up the scratches. 
They have since been abraded to a smooth surface, much of the 
de posit having been removed, so that the dark colour of the original 
flint shows through on the prominent ridges. 
The implements are very varied in form, and in the style of 
working; some, especially those of the ovate pointed type, are 
cleverly flaked, in this respect resembling neoliths. Others are 
exceedingly rude, almost shapeless, and difficult to recognise as 
having been wrought by man. In many, even of very rude type, 
it is nevertheless evident that care has been taken to form a good 
oint to the tool, and to secure such a wedge-shaped form as would 
render it suitable for fixing in a handle. 
: 
7 
' 
id 
| 
| Several examples of this phenomenon occur in the Knowle gravels. It 
is particularly well shown, however, in a large flint core, from Galley Hill, 
Kent, now, by the liberality of Mr. T. H. Powell, in the North Wilts Museum 
at Devizes. 
