TRANSACTIONS OF SECTION C. 545 



meable material that supports the wonderful supplies of water given by the Avbite 

 chalk in many areas, amongst others, the area pumped hy the Kent Water- 

 works, east of London, which raise about ten million gallons daily, and could 

 easily double that quantity ; while the chalk marl, in deep borings at many loca- 

 lities, has been found to be absolutely waterless, as at Kentish Town, Ilai-wich, 

 Southampton. 



The Cliffs at Lydden Spout were measured by Mr. F. G. Jlilton Price and 

 myself in 187G, and were described by Mr. Price in a paper on the beds between tlie 

 gault and upper clialk near Folkestone.' The height at this point was found to be 

 433 feet aboye the mean sea-leyel, and the thickness between the upper gault and 

 first bed of flints (the upper chalk) to be 348 feet. 



Of this thickness the lower white chalk forms the upper 150 feet ; the upper 

 part of this is the crate manieuse, and the lower part, the craie noduleuse, a 

 I. labiatus of Dr. Barrois ; the whole belongs to the Turonien of D'Orbigny ; 

 the lower 32 feet is the zone of Cardiaster pygmaus of JMr. Price, and is the ' grit 

 bed ' of local geologists, from its hardness being sufficient to turn the point of a 

 pickaxe ; the mass of the bed is made of comminuted fragments of inoceranii and 

 other fossils. The overlying bed is soft, but is not so pure a white as the upper 

 chalk; water can freely percolate through it, but it is doubtful whether much can 

 pass through the underlying 'grit bed.' 



Beneath is the junction bed, or zone of Bdemnifes pleinis of Mr. Price, four feet 

 in thickness : it is of soft texture, and dark yellowish colour, and is of a poorer 

 character. Below the junction bed is the grey chalk, 169 feet 9 inches thick, the 

 upper 55 feet in the zone of Belemnites idenus of Dr. Barrois ; the lower 93 feet is 

 the craie argileme avec bancs durs d ammonites rhotomagensis. The next 2 feet 

 9 inches is the well-marked ' cast bed,' which is marked and striped with mottlings 

 of a darker colour ; it contains a remarkable assemblage of fossils, which have some- 

 what of a gault facies, and it essentially marks the horizon of springs in this area ; 

 through it runs and issues the strong spring at Abbot's cliff, known as the Lydden 

 Spout, this formerly drove a water-wheel, giving the power required for a whiting 

 manufactory which once existed at the foot of the cliff; in later times it has pro- 

 vided water for the locomotives of the South-Easteru Railway. 



Below the ' cast bed' is 19 feet of marly chalk, forming the zones oi Ammonites 

 rhotomagensis and A. varians of Dr. Barrois. 



Beneath the marly bed forming the base of the ' grey chalk ' is the chloritic, or 

 rather glauconitic marl ; it is traversed by hard reefs of sponges, which are occa- 

 sionally converted into iron-pyrites, and are more or less entangled with the bones 

 of Ichthyosaurus ; it is the craie marneuse, with Flocoscyphia mmandrina of Dr. 

 Barrois. 



At Copt Point, the chloritic marl rests upon more sandy beds, which have beea 

 believed to represent the upper green sand of more western areas ; but, according to 

 Mr. Price and to Dr. Bari-ois, the facies it presents does not correspond with the upper 

 green sand of the West of England, but is essentially a part of the facies of the 

 chalk marl, and Mr. Price regards these sandy beds as the base of the chalk-marl, 

 and calls it the zone of Stauronema Carteri ; it is the equivalent of Pecten cwper of 

 Dr. Barrois, and on the horizon of the Warminster beds. 



In Normandy M. Hubert classes the grey chalk and sandy beds as cenomauien, 

 which he divides into three subdivisions : — 



Craie grise , . 16 m. = 52i feet 



Gres calcareux . . , . , . 18m.= 59 „ 



Glauconie sableuse 41 m. = 134^ „ 



246* 



The water absorbed by the porous white chalk of North-East Kent, from the 

 annual rainfall, follows the dip planes of the strata, and must circulate in the white 

 chalk under the sea ; and should the water be artificially abstracted in making the 

 proposed tunnel in St. Margaret's Bay, it must inevitably affect the existing water 



' Quart. Journ. Geol. Soc. vol. xxxiii. Part III. p. 431. 

 1882. N N 



