32 



MR. L. RICHARDSON ON THE RHJETIC OP [Eeb. I9II, 



emerges again near Greinton, to be re-discovered at Camel and 

 Sparkford Hills, which are probably part of its northern limb. 

 If this axis is traced on a geological map, the suggestion presents 

 itself that it is connected with the series of folds of which the 

 Mendip Hills is one, such an equidistance therefrom does it preserve. 

 In this area the sections that should be visited are those in the 

 railway-cuttings at Dunball and Cossington and in the quarries at 

 Catcott, Windmill Hill, Butleigh, and Butleigh Hill. The following 

 table shows the thicknesses of the several subdivisions at the two 

 ends of the area — at Dunball and Charlton Mackrell. 



Table III, illustrating the Thicknesses oe the Subdivisions of the 

 Kh2etic Seeies in the Polden Hills. 



Approximate thicknesses in 

 ft. ins. at Dunball and in ft. ins. at Charlton. 

 r . r ? I. Watchet Beds 3 10 absent. 



2 \ II. Langport Beds 4 3 20 8 



^ MIL Cotham Beds 4 5 4 9 



I f IV. Westbury Beds 32 2 22 4 



L3 (. ? V. Sully Beds 10 absent. 



(ii) Stratigraphical details. — The deep railway-cutting at 

 Dunball, the 'Puriton Section' of Bristow & Etheridge, 1 admirably 

 displays the sequence from the Grey and Tea-green Marls to the Lias. 



The Grey and Tea-green Marls are exposed on the west side of 

 the cutting, at the commencement of the wall. Black shales are 

 seen above, up to a prominent limestone-band — Bed 9. This bed 

 is more accessible on the other (eastern) side of the cutting, where 

 indeed there is a continuous sequence up to the rubbly limestones 

 of the Langport Beds. Half-way towards the first bridge is 

 seen the Sun-Bed, succeeded by the presumed equivalents of the 

 Watchet Beds, which are in turn followed by the Paper-Shales ; 

 while beyond — on the same side of the cutting — come Liassic strata. 

 The last, however, are better exposed on the western side. 



The only published record of the Dunball section which contains 

 original information is by Bristow & Etheridge, and from it 

 the present record differs in but a few minor matters of fact. 

 An abbreviated edition of Bristow & Etheridge's record is given 

 in the recently-issued Geological Survey Memoir on ' The Geology 

 of the Quantock Hills, &c.' (1908, pp. 70-71), where it is stated 

 that Messrs. J. H. Blake, W. A. E. Ussher, & H. B. Woodward 

 remeasured the section and apparently discovered no discrepancies. 2 

 They make no advance, however, in the matter of subdividing the 

 Bheetic, not separating the greenish- grey marly beds below the 

 Cotham Marble from the ' White Lias.' 



The massive ' Bottom Lias ' is at once noticeable. No limestone 

 is recorded in the official section as parting the Paper-Shales from 

 the presumed Watchet Beds. Probably it was absent from the 



1 Vertical Sections, Sheet 46, No. 1, Geol. Surv. 1873. 



2 See also ' Jurassic Bocks of Britain — The Lias of England & Wales 

 Mem. Geol. Surv. vol. iii (1893) pp. 81-82. 



