and otJier Fossils, found near Chatham, 243 



this was covered over by a deposit of flints and clay, 6 ft. 

 thick, over vs^hich the alluvial and vegetable soil is placed. 

 The bones, &c., are not found contiguously, but scattered at 

 distances of from 2 ft. to 50 ft, battered, and a little water- 

 worn ; and afford one proof among a multitude of others of 

 a great revolution or catastrophe having completely altered 

 the face of the earth in this part. A description of that part 

 of the chalk formation which I have had opportunities of 

 observing frequently, and a brief account of the deposits that 

 lie upon it, may enable us to appreciate the nature, and per- 

 haps go some way towards ascertaining the cause, of that con- 

 vulsion which has modified this small portion of country ; 

 and, I presume, the whole of that portion also which is now, or 

 has been, covered by the chalk. From the river at Durham to 

 the hill above Detling is a distance of ^\e miles, and it is occu- 

 pied by a ridge of chalk hills, in height from 500 ft. to 

 600 ft. ; it is a portion of the southern edge of the London 

 basin. Following the river downwards, these hills gradually 

 decrease in height till we arrive at Rochester, below which 

 the chalk dips northerly under the river, and reappears on its 

 opposite bank. On the north-east of the town of Chatham 

 the chalk forms a long ridge, being the basset of the valley 

 before mentioned ; it gradually slopes in a northerly direction 

 to, and dips finally under, the river at the extremity of the 

 dockyard : this is a distance altogether of five miles. From 

 Detling Hill to Upchurch, in a north-east direction, the dis- 

 tance is also five miles. This tract, for about half a mile's dis- 

 tance, is overspread with a stiff red clay, mingled with great 

 quantities of displaced flints, broken, but not rounded. The 

 remainder of it is occupied by the sands and clay of the plas- 

 tic clay formation, the thickness of the beds of which at and 

 near IJpchurch is more than 100 ft. From Upchurch to the 

 dockyard is a distance of 4^ miles : this line is along the 

 river and its marshes, and is all occupied by the plastic clay, 

 sands, and gravel. The depth of the deposits thus covering 

 the water-worn surface of the chalk does not generally 

 exceed 4 or 5 ft., except where the members of the plastic 

 clay occur in situ, which is towards the banks of the river, 

 when their thickness sometimes equals what has been men- 

 tioned. 



The first thing which strikes a geological observer in this 

 district is the destruction of the continuity of the chalk range, 

 and the passage of the river through the deep valley formed 

 by that act. The next phenomena are the formation of trans- 

 verse valleys, exhibiting on one side a 'basset of the chalk, 



R 2 



