CHALK WITH nnLEMNITELLV QUADRATA. 305 



noHced, however, that in the specimens examined h}' "Nfr. Player, 

 the proportion of phosphate in the washed brown grains did not 

 exceed 50 per cent. 



Lastly, Mr. Player remarks that the phosphate of lime in the 

 Taplow Chalk occurs in such a condition that it would not impro- 

 bably serve as a valuable fertilizer in its raw state, and without 

 undergoing conversion into superphosphate. Its condition is pro- 

 bably due to the incompleteness of the replacement of the carbonate 

 by phosphate of lime in the organisms. The removal of the former 

 leaves the phosphate in a honeycombed state, peculiarly open to the 

 attack of soil-acids. 



At present the phosphatic chalk has not been seen beyond the 

 limits of the pit at Taplow Court Lodge. There can be little doubt 

 that it underlies a considerable part, if not all, of the outlier of 

 Tertiary strata on which Taplow stands, but there are no other 

 sections to prove its extension. At the northern end of the outlier, 

 about 400 yards west of the Rectory, flinty non-phosphatic chalk is 

 exposed under gravel with a trace of Tertiary strata, which evidently 

 come on in force close by. A gravel pit 300 yards west of Taplow 

 Station also shows under the gravel a trace of Tertiary beds resting 

 on flinty chalk of the usual character. The east-south-easterly dip 

 of the strata about Taplow Court, if continued, would suggest that 

 in both these cases the flinty chalk exposed may lie above the 

 phosphatic zone. On the other hand, on the western side of the 

 outlier, a great thickness of flinty chalk has been laid bare in the 

 Root-House Pit, and almost certainly lies at a lower horizon than 

 the phosphatic chalk. The lower part of the northern end of the 

 pit exposes a nodular band resembling Chalk Rock, while one mile 

 farther north a small pit shows a rock of the character of Middle 

 Chalk. 



The next nearest exposure of the junction of the Tertiary strata 

 and the Chalk occurs at Pant's Hill, 400 yards north-north-east of 

 Eurnham Grove, and 2| miles north-east of the Lodge Pit. There 

 the Chalk contains but one layer of flints near the top, but a pale 

 greenish layer about 5 feet down. A thickness of about 8 feet of 

 chalk is exposed, but none of the rock possesses the characters of the 

 phosphatic chalk of Taplow. 



Westward from Taplow, along the Great Western Railway as far 

 as Buscomb, on the eastern slope of Kuowl Hill, at Pinkney's Green, 

 and around the Cookham-Dean outlier, the chalk is of the usual flinty 

 character up to the base of the Tertiary strata. The same remark 

 applies to the neighbourhood of Hedgerley, Harefield, Rickmans- 

 worth, and Watford, one of the sections at Harefleld giving an open 

 view of the topmost Chalk to a depth of at least 60 feet below the 

 Reading Beds. 



The evidence therefore tends to show that the phosphatic chalk 

 is of strictly local occurrence. Its disappearance may be due either 

 to its passing into chalk of the usual type, or to its being overlapped 

 in every direction by Tertiary beds. A fact which tells against the 

 former supposition is that we have not seen any chalk approaching 



