A HISTORY OF KENT 



With the great white cliffs of this remarkable formation fronting the 

 Channel at the nearest point of approach of our shores to the continent, 

 in full view of all those who pass through this gateway of our seas, and 

 with the bold scarp of the North Downs, which marks its prolongation 

 into the interior no less conspicuous to the pilgrim by land, no other 

 feature could indeed be more impressively characteristic of the county. 



The Downs form the highest ground in Kent, reaching elevations 

 of between 700 and 800 feet in its western part, and 600 to 700 feet 

 farther eastward. These heights are attained close to the steep escarp- 

 ment in which the Chalk terminates, the surface declining thence 

 gradually northward. 



It would be superfluous to describe the general aspect of the forma- 

 tion, but we may dwell for a moment on the remarkably homogeneous 

 composition of the Chalk, which is one of its most extraordinary features. 

 Throughout the whole of its extent in England, from its lowest to its 

 highest beds, with a thickness in some places reaching from 1,000 to 

 1,500 feet, and from its first appearance in the cliffs of the English 

 Channel to its disappearance in Flamborough Head and the Yorkshire 

 Wolds, this peculiar white limestone preserves everywhere its identity of 

 character, with such minor modifications of structure as become apparent 

 only when the formation is closely studied. It is one of the common- 

 place ' wonders ' of geology that this huge mass has been built up almost 

 entirely from the remains of lime-secreting organisms, among which the 

 minute shells of foraminifera are especially abundant. For a period of 

 time which is admitted to have been long even by geological measure- 

 ment, and by any standard of human history would be reckoned inter- 

 minable, the calcareous ooze derived from generation after generation of 

 these organisms slowly accumulated on the floor of an open sea, too far 

 from the coast to receive more than an inconsiderable sprinkling of 

 current-borne detritus, and that usually of the lightest. At rare intervals 

 however stones rafted from the land, perhaps by floating ice or entangled 

 in the roots of seaweed or of fallen trees, were dropped to the sea bottom; 

 and are occasionally found in the Chalk, as for example in the neighbour- 

 hood of Gravesend,^ but their occurrence is quite exceptional. Nodules 

 of flint, often occurring abundantly in bands or in tabular masses, are 

 characteristic of a large part of the Chalk and form an integral portion 

 of the deposit. Like the cherts of the Lower Greensand, their material 

 has been mainly derived from the siliceous spicules of sponges, which 

 are known to have flourished in large numbers in the seas of the period. 



Subdivisions of the Chalk. — The subdivision of this great mass into 

 Lower, Middle, and Upper Chalk was originally based mainly upon 

 slight differences of composition — the Lower Chalk being usually some- 

 what grey in colour, marly in its lower portion, and devoid of flints ; 

 the Middle division, white and rather flinty in places, sometimes with 

 a hard rock-band (the 'Chalk Rock') at the top ; and the Upper Chalk, 



' Mem. Geo!. Survey, 'Geology of London,' i. 82. 

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