228 THE GEOLOGICAL STRUCTURE OF THE 



as a consequence have given far too great a vertical thick- 

 ness to the " Inferior Oolite." The latter result of course 

 obtains more at Maes Knoll than elsewhere, because there 

 only a very thin capping of strata of Bathonian age is left 

 to represent the " Inferior Oolite." 



(2) Comparison of Sanders' Map ^ with our own. 

 Commencing at the main road, as before, Sanders shows 

 the base of the Inferior Oolite at the top of the Marl stone ; 

 then going west the line rises, and is carried along about 

 the middle of the Dumortieria-heds all round the hill until 

 it meets the main road at the south, by Elton Farm, when 

 it drops to the Marlstone level. Thence it is carried at this 

 horizon until a little east of Watercress Farm, on the 

 southern flank of the East Dundry Yale. Here it begins 

 to rise gradually, and at the head of the valley, at the 

 Butchers' Arms, it reaches the top of the Dumortieria-heds, 

 so that here it coincides with our own map and differs 

 seriously from that of the Survey. Returning, on the north 

 flank of this valley, it drops to the Marlstone level just 

 before East Dundry is reached, and along that horizon it is 

 continued until above Northwick Cottages. Here Sanders' 

 Inferior-Oolite line makes a large outward bend, as much 

 as 500 yards outside our Marlstone limit. Then it returns 

 to the Marlstone limit, at about the middle of the bend 

 before reaching Maes Knoll, and is carried at about this 

 level round the hill until the main road on the northern 

 flank is again reached. It does not show that great bend 

 at this point which is so conspicuous on the Survey 

 map. 



1 Sanders, William : ' Coalfields of Bristol and the Country adjacent 

 geologically surveyed.' Folio manuscript, 1862. Map published on the 

 scale of 4 inches to 1 mile ; republished by Lavars & Co., Bristol, on the 

 scale of 1 inch to 1 mile. 



