544, PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 8, 
’ The old sea-bed of the Sussex level, then, appears to pass between 
the old coast-line thus marked out on the north, and the beach- 
deposits of the Foreland, St. Helens, &c. along the coast of the Isle 
of Wight, becoming more like a river-gravel in character, and con- 
taining numerous flint implements in its westward extension. The 
supposition that there was here an estuary through which the rivers 
from the westward reached the sea when the Isle of Wight was 
still joined to the mainland, derives support from other. consider- 
ations. 
(a) The connexion ‘of the island with the mainland, which is 
obviously suggested by the continuation of the chalk range of 
Purbeck through the island, appears to have existed down to recent 
times. The ten-fathom line, which is within half a mile of the coast 
all along the back of the Isle of Wight, strikes across Christchurch 
and Poole Bays to Handfast Point, following the course of the 
vertical chalk strata, and again hugs the shore round the Purbeck 
coast. Inside this line the sea is generally less than five fathoms 
deep, and is steadily encroaching on the land at the rate of about a 
yard in a year. At this rate the coast would have receded from the 
line of the chalk to its present position in about 9000 years. This 
is of course but a rough estimate of time, but it shows the pro- 
bability of a connexion by which the Mammoth and tichorhine 
Rhinoceros had free access to the Isle of Wight down to the time of 
the lower valley-gravels, in which their remains are far from rare. 
. The Chines, or bunnies, along the coast between Hordwell and — 
Poole appear to show that a change has taken place in the course 
by which the streams reached the sea, as has been already pointed 
out. The extensive mud-flats more than a mile wide along the north 
shore of the Solent must, as Mr. Godwin-Austen has observed *, 
have originated in a very different condition of the Solent from the 
present, and they also point to the comparatively recent time at 
which the condition was that of an estuary, in which the formation 
of such mud-flats would have been natural. 
When a continuous range. of chalk downs stretched along where 
the ten-fathom line now lies between the Needles and Handfast 
Point, the river system was most probably analogous to that which 
now exists. All the streams which traverse the chalk of the Isle of 
Wight: and Purbeck, flow northwards from the older beds into the 
Tertiary basin; and it appears unlikely that the rivers which now 
enter the sea at Poole and Christchurch took an opposite course 
through the chalk. It is natural to suppose therefore that the Frome 
and Piddle continued their easterly course inside the chalk range in 
a joint stream, of which the Avon and Stour were aftluents, and 
which received tributaries draining country up to, and perhaps 
beyond, the chalk on the south, as the Corfe River, the Medina, and 
the Brading river still do. The rivers flowing into Southampton 
Water joined those coming from the westward by way of the Solent, 
and formed a broad estuary communicating with the sea by 
Spithead. 
* Quart. Journ. Geol. Soc. vol. xiii, p. 65. 
