Vol. 54.] NATUKAL GAS IN EAST STTSSHX. 567 



lY. Origin op the Gas. 



Appended to this paper are detailed descriptive sections of the 

 two wells at Waldroii (see pp. 569 & 570). The details show that 

 the borings commenced low down in the Ashdown Sands, traversed 

 the whole of those clay-beds below called the Pairhght Clays, and 

 extended into the ujDper beds of the Purbeck Series. 



The division between the Eairhght Clays and the Purbeck Beds 

 appeared to be fairly well marked off by a bed 5 feet in thickness, 

 composed of blue sandy marl-rock, containing bands of bituminous 

 shale and broken fossils. This bed was followed by a series of 

 shelly rocks which were penetrated to a depth of about 38 feet. 

 The following marine and brackish - water moUusca have been 

 identified in the series of rock-samples^: — Melania, Hydrobia {?), 

 Corhula oblata, Oyrena, Cardium, and Ostrea. None of these shells, 

 except Cyrena, occur in the Eairlight Clays. 



Note on the Mollusca. 



The writer considers that the appearance of the brackish-water 

 shells in the strata at the bottom of the Hastings Beds marks the 

 true horizon or junction between the so-called Sussex ' Purbecks ' 

 and the ' Hastings Beds,' and there is no other indication which can 

 be considered reliable. Thus the appearance of these brackish- 

 water forms denotes the commencement, or, more strictly speaking, 

 the termination of a transitional stage between the more marine 

 beds of the Lower ' Purbeck ' strata and the freshwater deposits of 

 the ' Hastings Beds.' There seems to have been a very gradual 

 passage ; and the writer is inclined to doubt that the Sussex 

 ' Purbecks ' can ever be properly subdivided into the Upper, Middle, 

 and Lower divisions of the Dorset series, since they never appear 

 to become so decidedly marine as the Middle Purbeck of Dorset. 

 It appears to him that the Wealden Beds and these Purbeck Beds 

 will eventually have to be grouped together under one head, since 

 they seem all to have had a common origin. 



Considerable misapprehension has been caused by the reported 

 discovery of brackish-water and marine shells in the lower horizons 

 of the Hastings Beds at Heathfield, Burwash, and Brightling 

 (Pounceford and Perch Hill). As a matter of fact, neither Mr. 

 Philip Rufford (of Hastings) nor the writer, who have made a con- 

 siderable study of these rocks, have ever discovered such shells in 

 the lower horizons of the Hasting Sands ; and we do not believe 

 them to exist. The truth seems to be that people have wandered 

 about collecting at Heathfield, Burwash, and Brightling, under the 

 impression that the fossils which they were discovering belonged to 



^ At a depth of between 339 and 377 feet. These beds were very uniform 

 in appearance and structure. 



