1 1 6 Geological Society. 



Wood on the banks of the Stour at Sutton ; and that described by 

 Mr. Brown at Copford near Colchester, which contains similar shells, 

 also bones of the ox and deer. Accumulations containing the same 

 testacea, occur at Grays near Purfleet, and at Southend in Essex, but 

 associated with remains of the elephant, rhinoceros, deer, ox, bear, 

 &c. In the bed at Grays rounded pebbles of chalk occur, agreeing 

 with those found in the diluvium, and from which they were probably 

 derived. 



Causes in Action. — In this division of the memoir are described, 

 1st, the alluvial accumulations ; 2ndly, the changes in the river 

 courses ; and 3rdly, the action of the sea on the coast. In illustration 

 of the two first, Mr. Clarke enters into a discussion on the supposed 

 position of the Roman station, Ad Ansam, and the alterations which 

 must have taken place, if the site assigned to it be correct. He then 

 proceeds to the action of the tides on the cliffs. 



His first acquaintance with the coast about Bawdsey was in 1814, 

 and between that period and 1829, a battery which once stood 100 

 yards beyond the present low-watermark, has been dismantled ; and 

 the life-boat house has been three times removed, to a distance at least 

 a quarter of a mile in rear of its original position. 



The destruction between the Aide and Bawdsey cliff during the last 

 20 years, is calculated to have been upwards of 100 acres ; and the 

 coast between that cliff and Bawdsey Haven, is stated to have dimi- 

 nished about two yards annually. Similar remarks apply to the cliff 

 between the Deben and Harwich harbour, batteries and martello 

 towers having been successively undermined. 



In 941 the church at Walton Naze was at a considerable distance 

 inland ; about 50 years since the church and burial-ground remained, 

 but not a vestige of either is left. In 885 a sea fight took place be- 

 tween Alfred and the Danes at the mouth of the Stour, where the 

 shingle bank now is. Harwich is also stated to have arisen in con- 

 sequence of the destruction of Orwell, which stood on the spot 

 called the West Rocks, and was overwhelmed by an inroad of the sea, 

 since the Conquest. During the period, however, that these destructive 

 changes have been proceeding on one side of Harwich harbour, 

 sandbanks have accumulated at another, and compelled the Stour 

 and the Orwell to open a new line of communication with the sea. 



The author then gives the following conclusions as deducible from 

 the statements in the body of the memoir. 



1. The substratum of the whole of Suffolk, Norfolk, and Essex is 

 chalk, which appears to have been dislocated and worn into deep hol- 

 lows by the action of water, previously to the commencement of the 

 tertiary era. 



2. On this abraded surface the plastic clays and sands were 

 formed, but not over the whole area. 



3. Partly on these beds and partly on the chalk, the London clay 

 was then deposited, but to no very great thickness. 



4. Upon the London and plastic clays as well as the chalk, the 

 crag was next accumulated in sandbanks, produced by the tidal waters, 

 and around projecting masses of chalk. 



5. While the crag still lay beneath the sea, a violent catastrophe 



