Mr. Lonsdale on the Oolitic District of Bath. 265 



belongs is extremely small. In some parts the oolitic beds are wanting, and 

 in others the presence of the formation is concealed by transported matter- 

 To the north of Calne the coral rag is bounded on the west by the brow of 

 the hills ranging from Lynham to Bencroft near Bremhill, and on the east by 

 a line passing from Preston to Hillmarton, Calne, and Quemerford. To the 

 south-west of Calne it is displayed in the denudation in which is situated 

 Bowood Park ; and it forms a narrow but continuous band by Studley, Derry 

 Hill, Red Hill, Bovvden Hill, Spy Park, Chitway, Sandridge, Bromham, Rovvde 

 Hill, Seend Bridge, and around the western side of the eminence on which 

 Seend is built. To the south of that village the coral rag attains a greater 

 superficial importance : the western boundary passes by Baldham Mill, Hinton, 

 Stourton Farm, and Rowd-Ashton Park to West Ashton ; and the eastern 

 extends from Hender's Copse by Keevil, and the north-western extremity of 

 Rey Down to Dunge. Between this hamlet and Westbury Field the forma- 

 tion is not visible, but it reappears at that locality, and constitutes a narrow 

 strip to the lane leading from Westbury Leigh to Brumridge Farm. Beyond 

 this point the coral rag is concealed by the overlying of other formations. 



Kimmeridge Clay. 



This great argillaceous deposit presents in Wiltshire no natural facilities 

 for examining its characters. It appears on the surface as a reddish brown 

 or lead-coloured clay, which has generally an unctuous feel, and occasionally 

 effervesces vividly with acids. When a small section is laid open, beds appear 

 both of a massive and fissile structure, and vary in colour from light grey to 

 almost black. The fissile or laminated property sometimes arises from the 

 presence of vegetable matter. Strata of a bituminous nature, and said to have 

 been used for fuel, were discovered in sinking a shaft at the brick-yard on 

 the north side of the Bath Road, near the foot of Devizes Hill. Towards the 

 top of the Kimmeridge clay irregular masses of argillaceous limestone occur, 

 inclosing fragments of shells, particularly of a thickly ribbed Ammonites : 

 blocks of sandy marlstone occupy a similar position ; and nodules of argilla- 

 ceous carbonate of iron are frequently met with. 



Ostrea deltoidea is the only fossil which I have found in a perfect state in 

 this formation. 



In the neighbourhood of Calne the Kimmeridge clay constitutes the greater 

 part of the low ridge near Sand's Farm, and a small denudated district which 

 may be included within a line drawn from Quemerford Bridge by Rough 

 Leaze, Stockley Common, Tossel's Farm, and around the western side 

 of the knowl on which is situated Pinhill's Farm, back to Quemerford. 



VOL. III. SECOND SERIES. 2 M 



