568 ME. C. DA.WSON ON THE DISCOVEKT OP [^^g* 1 898, 



the lowest beds of the Hastings Sands ; whereas it is clear to the local 

 observer, both from the localities named by these collectors and from 

 the appearance of the matrices in which these brackish-water forms 

 occur, that the specimens are obtained from the narrow strip of the 

 Sussex Purbeck Beds, which is exposed and has been so mapped by 

 the officers of the Geological Survey in. that neighbourhood. The 

 collectors have unconsciously strayed over the division-lines, and 

 specimens collected by them have been wrongly labelled as Wealden 

 forms in the principal museums of England. 



Okigin of the Gas (continued) 



Returning to the question of the origin of the gas found at 

 Heathfield, the writer considers that it is derived for the most part 

 from lower beds, either in the Purbeck Series or the Kimeridge 

 Clay. It is true that in most of the Wealden Group beds of lignite 

 occur of considerable thickness ^; but the phenomenon of spontaneous 

 gas-generation has never been recorded with respect to them. 

 Certain small beds of lignite actually occur in these borings ; but, 

 on glancing through the list of the rock-details appended, I do not 

 perceive any adequate source of this enormous accumulation of 

 gas.' 



Traces of petroleum and bituminous matter not uncommonly 

 occur in the Wealden Beds, but in no considerable quantity. The 

 Purbeck strata (Brightling Series) are a little richer, and it has even 

 been attempted to turn some of the bituminous shales between the 

 greys and the blues to practical account. Mr. E. Hallett, of Swifes 

 Farm, Burwash, had several tons of an unctuous blue clay, exposed 

 in a ghyll or valley near there, operated upon and extracted tar, and 

 subsequently a variety of products, such as pitch, grease, oil, naphtha, 

 and paraffin. But by far the richest supply of paraffin yet discovered 

 in the Sussex rocks, occurred in the Kimeridge strata, penetrated 

 by the Subwealden boring at Xetherfield in 1875. I learn from 

 Mr. Henry Willett that slight indications of petroleum were noticed 

 all through the Kimeridge Clay in this boring, but they became more 

 distinct at about 160 feet from the top of the clay (or 450 feet 

 from the surface)^ ; all below that depth was more or less impreg- 

 nated with petroleum, it being particularly abundant at the following 



1 See W. Topley, GeoL Surv. Mem. of the Weald, 1875, p. 347. The 

 thickest bed of lignite described at Waldron occurs in rocks higher than those 

 in -which the Heathfield Station boring was commenced. 



^ The foreman of the works said that the strata seemed full of it, for at least 

 100 feet. 



^ A great thickness of strata (about 500 feet) intervenes between the bottom 

 of the Heathfield borings and the horizon of the gas discovered in the Sub- 

 wealden boring. At the same time, it may be stated that in the American 

 natural gas-fields the gas has been proved to rise great distances above its 

 source — the distance depending entirely on the suitability of the structure of 

 rock. See Reports of the Departments of Geology of Indiana (1886-1894) 

 Pennsylvania (1886), Cahfornia (1897), and Ohio, vol. vi. 



