A HISTORY OF KENT 



of the county; but in the south the sea never lost its grip of the district 

 nor ceased to build up the framework of the present land. 



Atherjield Clay. — The first deposit of this sea was the Atherfield 

 Clay, so named from a locality on the coast of the Isle of Wight where 

 it is typically exposed, a brown or greenish blue clay, somewhat sandy 

 in places, containing numerous marine fossils such as Ammotiites, Nautilus, 

 Exogyra (an extinct oyster) and many other shells, with small crustaceans, 

 fish teeth and other remains. 



Owing to its soft perishable material, its comparatively slight thick- 

 ness, and the position of its outcrop on steep foundering slopes capped 

 by the harder overlying strata, it is rare that natural sections of this clay 

 are visible in Kent, though it was passed through in the railway tunnel 

 at Sevenoaks, and was in part recently exposed by artificial excavations 

 near the railway station at Hythe and at Bastead Mills near Plaxtole. 

 The mining shafts at Dover have however provided the most favourable 

 opportunity for studying this deposit in Kent ; its thickness here was 

 40 feet, the clay yielding large numbers of the characteristic fossils, and 

 its base resting with a sharp line of demarcation upon the Weald 

 Clay. 



Hythe Beds. — As shown in Table II., the term Lower Greensand is 

 generally extended to include the Atherfield Clay as well as the over- 

 lying sandy deposits, but is more strictly applicable to the latter. It has 

 reference to the prevalence of disseminated grains of glauconite, a green 

 silicate of iron, in the series. Near the surface however this mineral is 

 usually decomposed by weathering, giving rusty red or yellow tints to 

 the sandy rocks. These deposits, being less readily erosible, form bold 

 terraces or ' features ' at their outcrop ; fringing the northern border of 

 the low tract of Weald Clay, they constitute most of the rolling country 

 between this lowland and the North Downs, and include much of the 

 pleasantest inland scenery of the county. They represent the accumula- 

 tions of a shallow current-swept sea at a time when the land was not far 

 distant. The series is admirably exposed where intersected by the present 

 coast in the cliffs between Folkestone and Hythe, and the names of its 

 subdivisions are founded on these sections. 



The Hythe Beds, which constitute the lowest subdivision above the 

 Atherfield Clay, are composed of irregular alternations of slightly loamy 

 glauconitic semi-indurated sand (' hassock ') and hard sandy limestone. 

 These harder beds, known as ' Kentish Rag,' are extensively quarried for 

 building purposes and road mending at Hythe, Maidstone, Sevenoaks and 

 other places. They are frequently associated with thin layers of chert, 

 representing the nodular concentration of silica derived from the tiny 

 spicules composing the netted framework of the sponges that lived on 

 the old sea-floor. This chert, which is especially valued as a road material, 

 is most abundant in the upper part of the division on the high ground 

 south-west of Maidstone. Fossils are occasionally abundant in the Hythe 

 Beds, though rare in many localities. At Hythe the series has yielded 

 many echinoderms. Ammonites of several species. Nautilus, Belemnites of 



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