Geology of Wiltshire. 327 



is 70 feet in depth, and the stone when brought to the surface is 

 easily cut by the saw. Quarries have also been opened in Minch- 

 inharapton Common, Eisley Common, and Oakridge Common, at 

 the north-east side of which, and at Batllescomb, ihe basement beds 

 have been worked for roofing purposes; and further to the east, 

 at Baunton near Cirencester, the same false-bedded shelly oolites 

 are exposed to view in a quarry west of the turnpike road. 



The tipper zone consists of limestone of a blue colour, but 

 weathering white on exposure, in regular massive beds, and is 

 admirably exhibited in the deep cuttings on each side of the 

 smaller tunnel at Sapperton, on the Great Western Railway, where 

 it is 30 feet thick, dipping S.E. at 2". 



The main feature by which it may be distinguished from the 

 lower zone on the one hand, and the Forest marble on the other, 

 is the regularity of the bedding, and the more perfect character 

 of the fossils. Over an area of at least GO miles in length (already 

 mapped by the Survey), from Banbury to Corsham, and north- 

 wards to the borders of the Cotteswold range, this upper zone 

 everywhere presents the character of an evenly bedded white lime- 

 stone, and is generally so hard as to be eagerly sought for, in pre- 

 ference to any other rooks of the neighbourhood, as road material. 

 The absence of false bedding, and the usually perfect state of the 

 fossils as contrasted with those of the lower zone and of the Forest 

 marble, are features of importance, not to be disregarded when 

 treating of the sub-divisions of the Oolites. They show that 

 physical changes had intervened, producing over these regions, in 

 the present case, a sea of a tranquil character; and that, durin;^ 

 the deposition of the earlier and later stages of the Great 

 Oolite, the sediments were influenced by marine currents, 

 and other causes that produce irregular stratification or false 

 bedding. 



The juncton of these zones is generally well defined, and can be 

 observed in a quarry at Yatton Kennel near Corsham, in which 

 we find the following section. 



