448 



THE GEOLOGIST. 



The plienomenn of tliese deposits offer a wide scope for considera- 

 tion. The causes of such an accumulation of sedimentary matter, 

 the deposit of such matter anterior to the clay, and the water-worn 

 faces of the bluffs, could not have occurred in the present state of 

 the surrounding country. The rush of water necessary for such 

 events must have had a source much greater than any now existing 

 in the district, and perhaps far distant. The quantity of water must 

 have been vast. The conjecture that England at one time joined the 

 continent, and that the mountains of the continent were the sources 

 from which the supply proceeded, is therefore probable. It is very 

 interesting to find that the waters of the Medway deposit now a 

 sediment very similar to the clay filling up the faults and covering 

 the highest parts of the rocks. The larger debris brought down by 

 the river is also analogous to the gravel. I am thus led to the infer- 

 ence that these deposits are the relics of water having considerable 

 motive power. 



The principal sources of the Medway are now in the elevated por- 

 tions of the Weald, but we cannot attribute the ancient "diluvial " 

 waters to so limited a source. 



The lines of fracture, which constitute the principal faults, are 

 parallel to the course of the Medway, and are filled almost entirely 

 with clay (brick-earth), and contain the remains of m.ammalia, viz. 

 elephant, deer, horse, and hippopotamus. The bones and teeth are 

 found at a considerable depth in the clay, and much separated. I 

 discovered a fragment of a jaw of a horse with five teeth in their 

 sockets. There occurs also, at a depth varying from ten to twenty 

 feet from the surface, a bed of freshwater shells, Lymncea, Helix, 

 and Fupa. These shells are rather sparingly distributed, but may 

 be found in all the clay-pits worked on each side of the river. The 

 general level of the bed is about a hundred feet above the present 

 level of the water. Transverse faults cross the main lines of frac- 

 ture, and these are filled with a gravelly drift of flints, chert, and 

 ragstone, more or less water-worn ferruginous sand, and occasionally 

 a boulder of Druid sandstone. In the gravelly detritus I have found 

 detached fossils from the Lower Greensand. 



The following statement of the moving power of water, in the ' Civil 

 Engineers' and Architects' Journal,' gives the rates of the force required 

 for the disturbance of matter subjected to its action : — " A velocity of 

 three inches per second at bottom will work upon fine clay ; six inches 

 will lift fine sand ; eight inches per second, sand as coarse as linseed ; 

 twelve inches per second will sweep along fine gravel; and twenty-four 

 inches per second, gravel one inch in diameter." Erom the above 

 facts it would appear that the clay, drift-gravel, etc., were not de- 

 posited by the same forces, and consequently not at the same time. 

 The red clay, composed of very fine particles, was deposited after 

 the erosion of the rock. At that period, I presume, a great flow of 

 water was wearing away the angles of those rocks which obstructed its 

 course. When this speed diminished and the water became tranquil, 

 the fine clay held in suspension deposited itself ai} the bottom ; this 



