284 JURASSIC. 



local changes of condition, and in some cases perhaps to paucity 

 of sediment ; for there are no positive evidences over any extensive 

 area of the removal of any absent division, by denudation in 

 Oolitic times. 



Most of the strata are truly marine in the western and midland 

 counties, but there are in Yorkshire especially, evidences of estua- 

 rine conditions pointing to the proximity of rivers ; and, as 

 observed by Prof. Phillips, in that county the strata give evidence 

 of a true coal-field in the Oolitic era, produced by the interposition 

 of vast quantities of sedimentary deposits brought down by floods 

 from the land, between the more exclusively marine strata of the 

 ordinary Oolitic type. Thus while in the midland and southern 

 counties the Oolites yield many famous building-stones, in York- 

 shire the beds are rich in ironstone, layers of coal, beds of gritstone, 

 and shale. 



The Oolitic strata of the south of England were taken as the 

 types by William Smith ;^ but even in 1822 Conybeare and Phillips 

 questioned whether these divisions could be traced throughout the 

 course of the Oolites." The followino: are the main divisions : — 



Upper 

 Oolitic 



Purbeck Beds. 



Portland Beds. 



Kimeridge Clay. 

 Middle ( Corallian Beds. 



Oolitic. ( Oxford Clay and Kellaways Rock (Callovian). 

 Lower ( Great Oolite Series (Bathonian). 

 Oolitic. ( Inferior Oolite Series (Bajocian).^ 



The distinct groupings and nomenclature adopted for the Lower Oolites in 

 different parts of the country will be noted further on. The divisions into Upper, 

 Middle, and Lower Oolites are simply made for convenience, as they do not mark 

 any sharply-defined groups. 



The Oolites stretch across the country from Yorkshire to Dorset- 

 shire, forming often fine and bold hills, such as the Hambledon and 

 Howardian Hills in Yorkshire, the Cliff in Lincolnshire, and the 

 Cotteswold Hills in Gloucestershire. The stone-beds stand out in 

 prominent ridges, above the vales of clay ; and perhaps the series 

 of escarpments formed by the Portland Beds, Corallian Rocks, 

 Forest Marble, Fullers Earth Rock, and Liferior Oolite, is nowhere 

 better marked in succession than in the country traversed by the 

 London and South-Western Railway between Dinton, west of 

 Salisbury, and Yeovil. Excellent sections of the strata are exposed 

 in the cliffs of Yorkshire and Dorsetshire. In Yorkshire the hillv 



1 See Rev. Joseph Townsend, The Character of Moses, 1813 ; W. Smith, 

 Strata Identified by Organized Fossils, l8l6; Stratigraphical System of Organized 

 Fossils, 181 7. 



^ Outlines of the Geol. England and Wales, p. 202 ; see also Fitton, T. G. S. 

 (2), iv. 208. 



^ The term Bajocian, from Bayeux (Bajocea) in Calvados, was applied by 

 D'Orbigny to the Inferior Oolite and Fuller's Earth. 



