and Marlborough Railways 



175 



at Heywood, Bradley and Trowbridge, which are laid down 

 in the Ordnance Geological Survey Map. It might also be 

 connected with disturbance along the anticlinal line of the 

 valley. 



Two singular ravines are crossed by the railway, one atTinkfield, 

 and the other and larger one, a quarter mile nearer Devizes at 

 Nurstead. The peat and chalky mud in the former was pierced 

 for a considerable depth without finding a bottom, and on cutting 

 into the side of the ravine a curious section was presented. The 



Upper-green-sand was overlaid 

 by a chalky mud like pipe cla}% 

 this by peat containing wood and 

 nuts, and this by Upper-green- 

 sand not differing in appear- 

 ance from Upper-green-sand in 

 situ. It must however have been 

 green-sand washed down over the 

 peat, as shown in fig. 3. 

 The bottom of the ravine at Nurstead was laid open by trenches, 

 but the mud with chalky seams and pebbles, which covered the 

 bottom was not penetrated. The cutting for the road under the 

 Railway to the east of the ravine, was made through a bed of Gry- 

 phcea vesiculosa, and Exogyra conica, in clusters of shells which 

 had apparently been drifted together after death. 



The cuttings near Devizes are through the middle beds of the 

 Upper-green-sand, and yielded the fossils enumerated in the table 

 appended. I am almost entirely indebted to Mr Cunnington for 

 the list of Devizes fossils, and also for assistance in naming 

 others. Mr. Etheridge of the Museum of Practical Geology has 

 also given me his valuable help, by identifying many of the 

 species. 



Although foreign to the subject of this paper the great depth of the 

 old ditch round the keep of Devizes Castle may here be mentioned. 

 It had nearly vertical sides, and was 45 feet deeper than the present 

 moat in the Castle Grounds, that is, nearly as deep as the valley 

 between the Castle and Devizes Station. 



a Upper-green-sand, b Chalky mud. c Peat. 

 d Drifted green-sand. 



