1865.] 



FOSTER AIv'D TOPLET MEDWAY GEAVELS. 



447 



at all heights, from the present alluvial plain up to 300 feet above 

 it. It is not possible to draw any exact line between the higher 

 and lower gravels. They form, as Mr. Prestwich says, " the ex- 

 tremes of a series." Much confusion has arisen in consequence of 

 some observers emj)loying the term " high-level gravel " to designate 

 the higher teri-ace- or river-gravel of a country, whether occurring 

 on the flanks of a valley or capping the neighbouring hills, whilst 

 others restrict the term to the still higher gravels, which have no 

 obvious connexion with the present drainage of the country. 



The following table shows at a glance the terms used by some of 

 the most recent writers on the subject : — 



Prestwich, 1862*, 1863t. 

 Lyell, 1863t 



Prestwich, 1863t, 1864§. 

 Lyell, 186511. 



Whitaker, 18641[. 



Upland loams and gravels 

 (LyeU). 



High-level gravels 



Low-level gravels 



High-level valley-gravels 

 Low-level valley-gravels 



High-level gravels. 



1 r 



I Terra«e-gravels. 

 = I Low-level gravels. 



> L 



River-gravel and brick-earth are found overlying all the forma- 

 tions over which the Medway passes, sometimes forming broad 

 spreads, in other cases existing only in small isolated patches. The 

 most convenient way of treating the subject will be, in the first 

 place, to describe the gravel and brick-earth of the Medway and its 

 tributaries ; then, to pass on to a special description of the pipes of 

 gravel and brick- earth that occur in the Kentish E.ag ; and finally 

 to notice a few interesting cases of disturbance. 



a. The Medway. — The lowest gravel is seen at many places along 

 both banks of the Medway. In the Hastings Sand country it gene- 

 rally consists entirely of pebbles of Wealden sandstone, but in other 

 parts it often contains angular and subangular flints. Tertiary peb- 

 bles, and "Wealden pebbles. 



In some gravel at Maidstone, a few feet above the river. Professor 

 Morris has found numerous species of land shells**. 



The higher river-gravel of the Medway valley is far more inter- 

 esting and important than that which occurs at a low level ; it often 

 lies in terraces, and is found at various levels above the river up to 

 300 feet ; and, like the lower gravel, it always consists of rocks 

 which occur within the Wealden area. 



In following the Medway from its source we do not meet with 

 any gravel of great importance until we reach the neighbourhood of 



* Proc. Royal Soc. vol. xii. p. 38. 

 t Quart. Journ. Geol. Soc. vol. xix. p. 497. 

 I Phil. Trans, vol. cliv. 1864, p. 247. 

 il ' Elements of Geology,' 6th ed. p. 114. 

 ^ ' Mem. Geol. Survey,' Sheet 7, p. 68. 

 ** Mag. Nat. Hist. vol. is. 1836, p. 593. 



X ' Antiquity of Man,' p. 107. 



2 a2 



