326 



JURASSIC. 



Septaria have been polished as marble at Weymouth, and at Melbury Osmond,. 

 near Yetminster (Melbury Marble), and other places in Dorsetshire, where they are 

 locally termed ' turtle-stones ' or 'pudding-stone.' They there contain veins of 

 semi-transparent yellow calc-spar. 



The Oxford Clay is largely worked for brick- and tile-making ; and the clay 

 associated with the Kellaways Rock is also worked, at Oundle and other places. 



Beds of bituminous shale and lignite have led to futile searches for coal in many 

 tracts where the Oxford Clay is exposed ; as near Malmesbury,^ and near South 

 Brewham, north-east of Bruton.- At Studley, south of Trowbridge, bituminous 

 shale has been met with that emitted a brilliant gas when burnt. ^ 



The Kellaways Rock is used for building-purposes in some places, also for road- 

 mending. At Hackness in Yorkshire, the compact brown sandstones (Hackness 

 rock) are quarried. In this district the Kellaways Rock contains clayey sandstone 

 and ironstone, and the Killing Pits in Goathland Beck are considered to be the 

 remains of rude mining operations in the beds. 



The Oxford Clay is a retentive formation, and to obtain well-water it is necessaiy 

 to penetrate it, or to sink into the Kellaways Rock. Saline waters have been met 

 with at Salt's Hole, between Cricklade and Purton.* 



CORALLIAN BEDS. 



To this series the name ' Coral Rag and Pisolite ' was given by 

 William Smith in 1 8 1 5, on account of the local abundance of Corals 

 and the presence of pisolitic beds in Wiltshire ; but the term 

 Corallian, a modification suggested by D'Orbigny, is now usually 

 adopted. Originally the beds were divided by John Phillips (1829) 

 into : — 



3. Upper Calcareous Grit. 



2. Coral Rag or Coralline Oolite (Oxford Oolite of Fitton, 



1827^). 

 I. Lower Calcareous Grit. 



This classification was taken from the strata in Yorkshire, and 

 applied, so far as possible, to the rocks that extend thence to the 

 Dorsetshire coast near Weymouth. The beds are extremely variable ; 

 but taking Yorkshire as their type, the following general divisions 

 have been made in the series by Messrs. W. H. Hudleston and J. 

 F. Blake, to whom we are most largely indebted for our knowledge 

 of these rocks : '^ — 



F. Upper Calcareous Grit. 



E. Coral Rag. Sub-zone of Cidaris florigemnia. \ Zone of 

 D. Coralline Oolite. > Avimo7ntcs 



C. Middle Calcareous Grit. ) pUcatilis. 



B. Lower Limestone. 



A. Lower Calcareous Grit. 



Zone of 

 / Aninwuiics 



perar?)iat!(s 



^ J. Buckman, Q. J. xiv. 125 ; Geologist, i. 185. 



2 Memoirs of W. Smith, by J. Phillips, p. 66 j Conybeare and Phillips, GeoL 

 Engl., p. 195. 



3 R, N. Mantell, Q. J. vi. 312. * Q. J. xlii. 300. 



s See T. G. S. (2), iv. 20S. ^ q_ j. xxxiii. 389. 



