Mr. Lonsdale on the Oolitic District of Bath. 249 



(1 h.) The rubbly stratum is not of universal occurrence. The masses of 

 crystaHized carbonate of lime^ of which it is principally composed, present 

 invariably traces of an organic origin. A species of Astrea is the prevailing 

 fossil. The interstices between the crystalline masses are filled with nodules 

 of indurated marl. 



(1 c.) The hard, brown limestone, which is provincially called the hollow 

 bed, is strongly characterized by its colour, great toughness, and the hollow 

 casts of Trigonia coslata, Lima proboscidea, and numerous other shells. It 

 yields the greater part of the inferior oolite fossils. This stratum is apparently 

 equivalent with that of Dundry Hill, well known for its organic remains, and 

 for containing minute, globular particles of brown oxide of iron. 



(2.) The sand generally possesses only a slight degree of cohesiveness ; but 

 in some parts passes into a friable sandstone. The prevailing colour is yellow, 

 and minute spangles of mica are abundantly diffused through it. The calca- 

 reous concretions, or "^'sand burrs," are very tough, and frequently contain in 

 their centre the casts of Ammonites and other organic bodies. This division 

 of the inferior oolite thins out towards the south-west boundary of the forma- 

 tion ; and is wanting at Frome, Radstock, and Tunley. 



The superficial extent of the inferior oolite in the district to which this 

 memoir belongs, is small. The formation may be described as constituting 

 narrow zones circling around the sides of the hills, and occasionally extending 

 into promontories. Of these the most considerable are Beacon Hill, the ridge 

 advancing from Duncorn Hill to Tunley, and that from Huddock's Hill to 

 Clan Down. The inferior oolite likewise has several outliers; among which 

 may be enumerated, Stantonbury and Winsbury Hills, the Barrow Hills, 

 Priest Barrow, the Sleight, and the ridge to the south of Newton Park. The 

 most favourable point for examining the formation with the exception of the 

 rubbly stratum (1.6), is the banks of the canal opposite Limpley Stoke. 



The only deviation from the regular dip to the south-east, and not pro- 

 duced by faults, occurs near Kelston, where the inclination is to the south-west. 

 This deflection is owing to the dip of the lias towards the Keynsham valley. 



Fuller's Earth. 

 The inferior oolite is separated from the great oolite by a thick, argilla- 

 ceous deposit, which has been called the fuller's earth. The peculiar 

 mineral, from which it has derived its appellation, is confined to a particular 

 district ; and where it occurs, it constitutes but a very small portion of the 

 thickness of the formation. — The following table exhibits a general type of 

 the fuller's earth. 



VOL. in. SECOND SERIES. 2 K 



