Purbeck series, 

 10 feet. 



418 PURBECK BEDS AND IRON-SAND. CHAP. 



strata at all, but in low ground occupied by Kimmeridge clay 

 on the eastern side of the hill. 



This clay appears in the deeply-cut hollow between Muswell 

 Hill and Brill, and is worked for bricks. Portland stone lies over 

 it ; then follows what represents the Purbeck beds ; and iron-sand 

 with its clays caps the whole. The whole line of road over Mus- 

 well Hill is explored by many pits which disclose the iron-sand 

 series in a satisfactory manner. If we combine the sections on the 

 whole line from Brill over Muswell Hill, the result will stand 

 thus : 



ft. in. 

 (~ Brown ferruginous rock, partly arenaceous, partly 



oolitic, with some bands of Cyrenae. 



Iron-sand series, I Ye llow and white sands, with clay bands, and iron 

 50 or 60 feet, bands< 



Brown ferruginous lumpy sandstone, with clay bands 

 L in places. 



White calcareous laminated band, marly or stony . I o 

 Grey argillaceous beds . . . . . .30 



White calcareous, marly or stony . . . .20 



Grey clay ..... ....06 



White laminated stone i o 



Grey clay ......... i o 



White stone i o 



Grey clay .........06 



One of these stone-beds is drilled on the upper surface by some 

 tubicolous animal ; the stone is occasionally close-grained, like the 

 ' curF of Hazeley. 



Portland rock below, in lumpy shelly masses of small thickness. 



On the line by Long Crendon to Thame are many excavations, 

 some of which shew traces of Purbeck beds and of the incumbent 

 ferruginous sands. The representative of the Purbeck beds is chiefly 

 clay, as in Shotover Hill ; but at Long Crendon the ' malm' rubble 

 of Garsington and Combe Wood is also seen above the Portland 

 rock. In the neighbourhood of Aylesbury the Purbeck beds again 

 become distinct, and are covered by white or ferruginous sands of 

 considerable thickness about Hartwell, whence some was taken for 

 glass-making. At Dinton variously-coloured clays rest on lami- 

 nated stone and clays, the former compact or decomposed to ' malm/ 

 'with spiral univalves, small modiolse, and cyclas' (Fitton). At 

 Bishopstone, in the same neighbourhood, alternating clays and 

 limestones (one band of clay very dark) rest upon white marly 



