59 



paleontologically, in North-east France with the Upper Kim- 

 meridgian of Dorset. 



The Virgulian of the French geologists, according to 

 Huddleston, corresponds with the upper beds of the Lower Kim- 

 meridge Clay of Dorset, wherein Exogyra virgula, the type fossil,, 

 first appears, as the beds are considered from above downwards. 

 The Dorset Virgulian beds are developed in Kimmeridge Bay 

 between Hen Cliff and Brandy Bay, where the uplift effecting the 

 Purbeck Anticline has its axis cut by the coastline. 



The bituminous shales are found in the Upper Kimmeridgian 

 of Dorset and at similar horizons throughout the belt across the 

 Midlands, but outside Purbeck nothing much has been done at 

 any time in the way of mining. The Kimmeridge Shales con- 

 cealed beneath the Weald are almost certainly rich in bituminous 

 seams. The natural gas of Heathfield demonstrates the presence 

 of gas, there stored in the Hastings Sands and most probably 

 derived by natural distillation from the Kimmeridge Clay below. 

 This supply was at one time used to illuminate the railway station, 

 and it was even proposed to light Eastbourne from it. Oil oozes 

 out in small quantities from the Kimmeridge shale dug from the 

 Norfolk seams. With these exceptions the bituminous shale yields 

 gas or oil distillates only on heating, the bituminous substance, 

 whatever it is, being held in some sort of combination or intimate 

 mixture with the inorganic matrix of the shale. 



While reserving the fuller discussion of the origin of 

 petroleums in general for a later part of the present series of 

 papers, it appears safe to affirm that the original sub- 

 stance of the Kimmeridge Oil was fully organic ; whether 

 purely animal in character or purely vegetable or a mixture of the 

 two is not certain. There are no indications whatsoever of vol- 

 canic action that might have spread mud charged with hydro- 

 carbons on the floor of the sea, as is suggested by one school, or 

 of any serious tectonic movements during Kimmeridgian times, 

 either in Dorset or elsewhere in Britain or the Continent, which 

 might have caused dykes to have opened out, along which 

 bituminous substance poured from below. The faults shown in 

 the sea-cliff sections are all post-Kimmeridgian ; some possibly 

 pre-Cretaceous and others of early or mid-Tertiary times. ' 



It is maintained by some that certain bituminous shales, akin 

 to Kimmeridge shales, are genetically related to the coal measures 

 that occur in the same deposits at identical or different horizons. 

 Both shale and gas coal have been worked for oil in various places 

 in the English and other coalfields. Kimmeridge Clav is one of 

 the many formations which comprise the Jurassic Svstem, in 

 which, in certain deposits of a littoral facies, as in East Yorkshire 

 and North Scotland, considerable quantities of coal derived from 

 a rich land vegetation are enclosed. Kimmeridge Clay itself in 

 Dorset and the Midlands generally is, however, a tvpical deposit 

 of a fairly deep and extensive sea, and does not ' contain any 

 recognisable plant remains. These were doubtless carried down 



