The Sub-Wealden Exploration. 263 



and calcareous stratum, of a light grey colour, which occurs at from 

 600 to 602 feet. This, when slightly warmed or struck, smells very 

 strongly of petroleum. At 604 feet there is again about 6 inches of 

 hard clay with similar characters. 



" Slight indications of petroleum have been noticed all through 

 the Kimmeridge Clay, but they become more distinct at about 160 

 feet from the top of the clay (or about 450 feet from the surface) ; 

 all below that depth is more or less impregnated with petroleum, it 

 being particularly abundant at the following depths (from surface) 

 —600, 604, 617, 622, and 651 feet. Fossils are scarce, or absent, 

 in those parts of the clay which are richest in petroleum. 



" Occasionally there have been veins of carbonate of lime crossing 

 the core obliquely ; these were especially abundant at 480 and 549 

 feet. The core readily breaks along these oblique lines. Some of 

 the strings of carbonate of lime are scarcely visible to the eye ; at 

 first it appears as though the beds in these parts were dipping at 

 considerable angles, and that the cores break along the lines of 

 bedding. But this is not the case ; all the beds yet passed through 

 are horizontal. 



" A list of the fossils hitherto observed is given below. Mr. E. 

 Etheridge, F.E.S., has kindly looked over some specimens about 

 which I felt doubtful ; the list of generic names here given may, 

 therefore, be taken as correct. When more specimens have been 

 collected, and time allows, we shall, no doubt, be able to add the 

 specific names to many. We seldom, however, obtain perfect shells, 

 and very frequently the part missing is just that part which is re- 

 quired in order to determine the species. 



" It has not yet been possible to make oiit any distinctive zones of 

 life, correlating the Kimmeridge Clay of the boring with that known 

 elsewhere. Even when all the cores are thoroughly examined, and 

 every species fully tabulated, this will be at best a very uncertain 

 task, for it is never safe to infer the absence of any fossil, at certain 

 horizons, from an examination of a vertical section only two inches 

 in diameter. 



" The comparative abundance or scarcity of certain shells is, 

 however, worth recording. Trigonia and Alaria are exceedingly 

 rare ; Ammonites biplex is tolerably abundant all through ; Cardium 

 also occurs all through, but most commonly in the higher part ; 

 Modiola pectinata occurs all through the clay, but in the upper part 

 the shells are small, and it is only in the lower part that full-sized 

 specimens have been obtained ; the same remarks apply to Lingula 

 ovalis. 



" The horny shells of Discina and Lingula are well preserved ; and 

 so, too, are the shells of Ostrea, Pecten, and Belemnite. The shells 

 of Ammonites, Modiola, Cardium, and Astarte, are generally less 

 perfectly preserved ; whilst Area, and some others, occur only as 

 impressions, but all the markings are plainly visible. 



" In the following list it will be seen that Gryphea virgula, the 

 shell so especially characteristic of the Kimmeridge Clay, is absent. 

 Although this shell has been carefully searched for, not one speciiaea 



