242 Mr. Lonsdale on the Oolitic District of Bath. 



nected by two plains. Of the former, the most western may be called the 

 ran^e of the great oolite. It rises abruptly from a denudated valley of lias, 

 and attains its greatest elevation at Lansdown, where its summit is 813 feet 

 above the level of the sea. Its general direction is north-east and south-west. 

 In the neighbourhood of Bath it is greatly intersected by deep and sinuous 

 valleys. The escarpment from Toghill near Wick, to the ridge above Wel- 

 lovv, consists of lias, inferior oolite, fuller's earth, and great oolite; but to 

 tiie southward of that point, the last formation is wanting, and tlie series is 

 composed of lias, inferior oolite, fuller's earth, and forest marble. 



The plain, which joins this range with that of the coral rag, preserves to 

 the north of the road from Bath towards Devizes a tolerably uniform incli- 

 nation, which nearly coincides with the dip of the strata of cornbrash and 

 Oxford clay composing the surface of the country : but between the road just 

 mentioned and Bradford, a sudden depression takes place, arising, appa- 

 rently, from an increased dip in the great oolite*. To the south of Brad- 

 ford the plain recovers its usual features, which it keeps to Beckington, where 

 it is disturbed by an elevated ridge of forest marble, extending transversely 

 from that village nearly to North Bradley. 



The second range, which it is proposed to designate by the name of coral 

 rag, rises precipitately from the Oxford clay valley, and has a direction nearly 

 parallel with the range of the great oolite. From Lynham to Bowden Hill 

 and Sandridge, it constitutes a prominent feature in the outline of the country, 

 and maintains an almost uniform elevation. At the latter point the western 

 continuation of the formations composing the ridge has been removed by de- 

 nudation; but to the south of the "Wilts and Berks canal, the surface again 

 rises, and a series of low hills extends from Seend to West Ashton, where they 

 decline to the level of the Oxford clay plain. The escarpment consists, 

 principally, of the Oxford clay, the calcareous grit, and the coral rag ; but the 

 Kimineridge clay and the lower greensand are superimposed at Bowden Hill 

 and Seend. 



The plain which unites the second range with the third, or that of the 

 chalk, varies greatly in its breadth. Between Keevil and Earl's Stoke the 

 width exceeds three miles, but between Westbury and Westbury Field it is 

 less than half a mile. From the last-mentioned town to Polshot the surface 

 is a nearly uniform flat, consisting of Kimmeridge clay, but to the north of 

 that village it is diversified by gentle undulations crowned with thin beds of 

 the lower greensand. The eastern boundary of the plain is formed by a 

 narrow band of gault. 



* Plate XXXII. Fig. 3. 



