228 On the Recent Discovery of Flint Implements 
that we ought to be able to point out the direction of the current 
of the ancient river, and also a sufficient obstacle to account for the 
still water on the north bank. 
A single glance at the position of the hill ranges will show, 
that a stream of water flowing down the valley of the Nadder 
from Wilton, will wash the base of the chalk and meet with the 
first impediment to its progress in the curve of the hill at East 
Harnham : the check thus produced would be but slight as compared 
to that it would experience by encountering a volume of water of 
greater velocity coming from the valley of the Avon. Then again 
the elevated wedge shaped ridge of chalk at Fisherton would act 
much in ths same way as the central column of a double arched 
bridge, behind which accumulates asmall heap of mud and sand. 
Here then is substantial proof of the causes which must have 
produced still water, and its concomitant mud on the north side of 
the valley, and a brisk current, with but little deposit, on the south 
bank. 
In like manner a careful examination will show the probable cur- 
rents and directions of the old representatives of the Avon, 
Nadder, Wiley and Bourne, throughout the entire length of their 
courses. 
As affording an excellent illustration of the eroding action of 
water, attention is particularly directed to the manner in which the 
curved outline of the chalk hills has been altered and worn away 
precisely at those points which offered the most resistance to the 
onward flow of a body of water, this is perhaps nowhere so well 
shown asin the valley of the Avon between the villages of Stratford 
and Amesbury, particularly at Durnford and Heale. Here it is 
most marked and indicates that the stream flowed in one direction 
only. 
Of the third class or low level gravels, I shall say nothing 
further than that up to the present time no implements, and but 
very few organic remains have been found in them near Salisbury, 
although a large quantity of this gravel has been dug for road 
purposes, and most careful search has been made both by myself 
and other geologists. On the Continent and other parts of 
