224 On the Recent Discovery of Flint Implements 
joins a small stream called the Bourne, and forms a kind of 
buttress which separates the two valleys. It is however separated 
from the main tract of high land by a transverse depression 
about 80 feet in depth, so that it forms an isolated hill en- 
tirely disconnected by valleys of greater or lesser depth, from 
any high ground. From this peculiar conformation it will 
be evident that when the gravel was deposited on Milford 
Hill, the ancient river would during the variations of its course 
have extended from Laverstock Hill on the east, to Harnham 
Hill on the west, a distance of about two miles. The drift at 
Milford completely invests the summit of the bill, is thickest at the 
top, where it attains a depth of from 10 to 12 feet, thins out gradually 
on the sides, and ceases altogether rather more than half-way 
down. It is quite free from anything like stratification, rests 
unconformably on the chalk, running down in many places into 
shallow pot holes. As measured by the aneroid, it is about 100 
feet above the present level of the river Avon. In many 
places there is at the base of the compact gravel, resting upon 
the chalk, an irregular deposit of pale fawn-coloured chalk- 
rubble, which contains a small admixture of flint gravel, but 
no organic remains, Some few years since, a good section of 
this drift was exposed on the south-eastern side of the hill ina 
cutting made for the London and South Western Railway; and 
here near the base of the gravel, a narrow seam of loose light 
coloured sand containing shells was discovered. The shells in this 
one spot existed in the greatest abundance, and although ex- 
tremely friable were generally unbroken. They consisted prin- 
cipally of Helix hispida in all stages of its growth, a few 
specimens of Helx arbustorum and a single individual of Zuwa 
subcylindrica. All these shells are terrestial, and in every way 
agree with examples of the same species still living in the 
adjacent fields. With the single exception of a fragment of 
an upper molar tooth of a species of Hguus, no bones or mammalian 
remains have as yet been discovered, either at Milford Hill or 
any high level gravel in this neighbourhood. At no other point 
in the gravel has any seam of sand containing shells been 
