94 SEVENTH REPORT—1837. 
chert, and appears to have a western origin ; but there are also in it 
fragments of tertiary pudding stone, and water-worn masses of grey 
weathers belonging to the plastic clay, the result of local degradation. 
This gravel has itself been subjected to erosion, the hollows having 
been filled up with transported matter of similar, though altered cha- 
racter. Sothat there is evidence here of two periods of drifts, and per- 
haps three currents, which were probably connected with three impulses 
of elevation. Mr. Clarke mentioned several facts relating to Poole 
harbour. The land is there gaining on the sea, the town now oceupy- 
ing ground where fifty years ago there was deep water; andin a well 
bored a year ago, about a furlong from the sea, in one of the streets, 
Mr. Clarke found at six feet below the surface, sea-weed, and a stake 
and post, evidently part of an old embankment. The Bar also, which 
lies off the entrance to the harbour, has advanced between 1785 and 
1829, (that is in forty-four years,) half a nautical mile, or about 
forty-six yards per annum ; and as it still continues to advance, and 
is now not a nautical mile from the cliffs of Old Harry, it is probable 
that unless a new channel can be made the harbour may in process 
of time be closed. The Dunes or Sand hills are on the increase, a 
new series having grown up in five years on the south side of the 
entrance, which rivals those of the north; and it is remarkable that 
the valleys in these dunes correspond with the prevailing winds; which 
points to the probability that the same cause may have operated in the 
ancient strata before their consolidation. That elevations and depres- 
sions have taken place within recent times on the shores of Poole Har- 
bour, may be proved by the occurrence of beds of peat at the very 
edge of, and in the water itself. The whole valley of the Bourne, 
for three miles from the sea, contains beds of peat from ten to twenty 
feet thick, with huge trees of oak, beech, hazel, &c., none of which now 
grow in the valley; and a Roman Via now terminates at about half a 
mile from the northern head of Hole’s Bay in what is now a marsh 
and extensive peat bog, although it can scarcely be supposed that this 
road could have had originally such a termination, the probability 
being that it led, at its formation, to a landing-place. 
On some Fossil Wood and Plants recently discovered by the Author of 
this Memoir low down in the G'rauwacke of Devon, being one of the 
results of an attempt to determine the relative age and order of the 
Culm/field and its Floriferous Shales and Sandstones. By the Rev. 
D. Wittiams, F.G.S. 
The author stated that he produced the specimens of fossil wood 
and plants in compliance with a recommendation of the committee of 
of the Geological Section of the Bristol Meeting. From his examina- 
tion of the strata in North Devon and the Quantock Hills, he had con- 
structed the following 
