7I8 MKSSES. S. S. BUCKMAN AND E. WILSON [Nov. T896, 



(1) Comparison of the Geological Survey Map l with the 

 one here presented. 



The Geological Survey map represents at Dundry only Inferior 

 Oolite resting upon Lower Lias. The boundary-line which we shall 

 have to notice is that drawn separating the deposits so classed. 

 Beginning at the main road on the northern flank of the hill, and going 

 westward, the Survey's boundary-line of Inferior Oolite coincides 

 with our own (beginning of deposition in Aalenian age), and is 

 drawn at the top of the Dumortieria-cla,ys, along by the village and 

 ' The Grove,' until about 250 yards north of Castle Farm, when it 

 strikes off to the top of the ' Cephalopod-' or ' bifrons-he&s ' ; and at 

 Castle Farm it is about 150 yards outside our line. It continues on 

 or a little below this horizon round the southern flank of the hill to 

 Rackledown Farm, when it drops below the Marlstone — as much 

 below, in fact, as it ought to be if the Marlstone were really the 

 Ironshot Oolite of the JSauzei hemera. It continues at this level 

 round both sides of the East Dundry Valley, with the result that the 

 Survey base-line of Inferior Oolite is, at the head of the valley, as 

 much as 650 yards outside ours. 



Their boundary-line then continues to run on this infra-Marlstone 

 level to Maes Knoll, where in drawing our line we differ from the 

 Survey to the extent of about 100 feet in vertical thickness, and in 

 some places, as at the north-eastern corner, to the extent of about 

 250 yards in horizontal distance. 



From Maes Knoll their boundary-line continues along the northern 

 flank of the hill on the infra-Marlstone level until it approaches the 

 main road whence we starter!, when they show a lengthy northward 

 prolongation of ' Inferior Oolite ' by the eastern side of the bend in the 

 main road. This projection is not only some 400 yards outside the 

 boundary of what they call Inferior Oolite across the road, but it is 

 even some 250 yards outside what we take to be the horizon of the 

 Marlstone. 



It will thus be seen that, except along the northern flank of 

 Dundry Hill, to the west of the main road, the Survey have mapped 

 far too great an area as Inferior Oolite, and as a consequence have 

 given too great a vertical thickness 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's Map 2 with our own. 



Commencing at the main road, as before, Sanders shows the base of 

 the Inferior Oolite at the top of the Marlstone ; then the line rises, 



1 Sheet XIX., ' Geological Information revised, and Penarth Beds surveyed, 

 by II. W. Bristow, H. B. Woodward, W. A. E. Ussher, and J. H. Blake, 1867- 

 1871. New edition. Published May 1873.' 



2 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 irch to 1 mile. 



