ON THE SUB-WEALDEN EXPLORATION, 23 
At the end of last year (1873), the contract with Mr. Bosworth (then the 
contractor) having expired, the work was handed over to the Diamond Rock 
Boring Company. By their system of boring long cores of strata are brought 
up, of which the mineral character and fossil contents can be ascertained with 
great accuracy*. 
The boring is now (August 1874) 1030 feet from the surface, but the lowest 
17 feet of core are not yet extracted. The strata from about 350 feet to 
1013 feet haye been examined with care, and many thousands of fossils or 
_ fragments of fossils have been observed. The greater part cannot be deter- 
mined at all ; in a large number of instances the genus only can be ascertained ; 
but several hundred specimens can be with certainty assigned to their 
respective species. I have to thank Mr. Etheridge for much assistance in 
determining the fossils. Mr. G. Sharman and Mr. E. T. Newton have also 
kindly given me their aid. To Mr. Davidson I am also much indebted; he 
has looked over and named the Brachiopoda, and has drawn specimens of 
Lingula ovalis and Discina latissima from the boring for the forthcoming 
Supplement to his ‘ Monograph on the Brachiopoda,’ published by the Paleon- 
tographical Society. 
The greater part of the cores have been broken up on the spot, and the 
fossils sorted out for more detailed examination in London. In this task I 
have often had the assistance of Mr. Willett and Mr. Peyton. Some of the 
cores have been broken up and examined by Mr. Willett at Brighton. 
- The greater part of the strata traversed below 290 feet is clay ; generally it 
is rather calcareous, and from 640 feet downwards there are bands of cement- 
stone. The higher part of the Kimmeridge Clay is rather sandy, but no beds at 
all approaching a sandstone in character have been observed in that formation. 
The middle and lower part of the Kimmeridge Clay contains much petro- 
leum ; at some horizons there is so much that the shale will burn. The petro- 
leum shales of the lower part are generally very fossiliferous; but those of 
higher portions are often very bare of life. 
The Oxford Clay often contains much petroleum, and it also is very fossili- 
ferous. 
Generally in England the Coral Rag comes between the Kimmeridge and 
Oxford Clays; this is also the case in the Boulonnais. Occasionally, however, 
in England the two clays come together without the intervention of the Coral 
Rag. ‘This appears to be the case in the boring. An Oxford-Clay fossil 
(Ammonites Sedqwickii, Pratt) was observed at 972 feet from the surface. 
Below this several imperfect specimens of ornate Ammonites occur. A good 
example of Am. Jason, Rein., occurred at 990 feet, and Am. Lamberti, Sow., at 
1000 feet. A fragment of Pollicipes (probably P. concinnus, Sow.) occurred 
at 993 feet, and a doubtful Gervilla at 998 feet. Pollicipes and Gervillia both 
occur in the Oxford Clay, but I believe have not yet been recorded from the 
Kimmeridge Clay of England. 
With regard to the exact point at which the Kimmeridge Clay leaves off 
and the Oxford Clay begins there is some doubt. We must be guided in 
this case by paleontological evidence, assigning all those strata to Oxford 
Clay which contain fossils only hitherto known from that formation, and 
doing the same with the Kimmeridge Clay. We have seen that an Oxford- 
Clay fossil (Ammonites Sedqwickii) occurs at 972 feet. Gryphea virgula, 
Defr., a Kimmeridge-Clay fossil, occurs at 950 feet ; this is therefore Kim- 
* It should be mentioned that other methods of boring (in holes of small diameter) 
succeed in extracting solid cores of strata; but probably no other would give such long and 
unbroken cores. : rm : 
