236 3Io7iis— Geological Excursion to Bath, fc. 



Am. Jason, Nucula, Avicula espansa, and which had been thought to 

 be of Liassic age. 



Another excursion included a visit to Eadstock, and the Mendips, 

 passing along the table land of the Great Oolite, on Odd Down, the 

 Fuller's earth was examined in a field cutting on the hill side, yielding 

 many Rhynclionella varmns, and other fossils. At Eadstock, the 

 White Lias and Lower Lias are fairly exposed, the zone of Spirifer 

 Walcottu, with Pholadomya in their normal position was carefully 

 examined, and it was interesting to observe that coal was won 

 through these beds, owing, as is well known, to the comparative 

 thinness of the Secondary strata in this area as compared with 

 similar beds south of the Mendips, and their unconformity to the 

 inclined and faulted Coal-measures below. Thus, according to Mr. 

 C. Moore, the relative thickness in the two areas is as follows : ^ — 





"Without Coal basin. 



Within Coal basin. 





feet. 





feet. 



Triassic beds 



... 2000 





50 



Rheetic beds 



50 





50 



Lower Lias 



700 





2 



Middle and Upper Lias ... 



600 





42 



Inferior Oolite 



170 





25 



3420 169 



Many fossil plants were collected, and the party had the pleasure 

 to examine the fine collection formed by Mr. J. McMurtrie, consisting 

 of Lepidodendrce, Sigillaria, Calamites, Aster ophyllites, and the ferns 

 Neuropteris and Pecopteris ; some specimens shewing the circinate 

 vernation, others traces of fructification, but all in a state of preser- 

 vation for which the Eadstock Coal-field is celebrated. 



Proceeding southward the Dolomitic conglomerate was seen near 

 Stratton, and further on the outcropping of the Lower Coal-measures, 

 the Millstone grit, and Carboniferous Limestone tilted up at a con- 

 siderable angle ; beyond this is the Old Eed Sandstone, which there 

 forms the crest of the Mendips, and at East End, near Stoke Lane, 

 are portions of a dyke of considerable thickness, emerging from 

 beneath the Old Eed Sandstone, occurring as bosses in the field, but, 

 traced for some distance over the district, it is conglomeratic in 

 places, and pronounced by Mr. D. Forbes to be Dolerite. 



This mass of igneous rock is considered by Mr. C. Moore to have 

 been the cause of the elevation of many thousand feet of stratified 

 rocks, and of the present anticlinal arrangement of the strata of the 

 Mendips. Beside this, Mr. Moore inferred an old land-area, as 

 originally suggested by Mr. Godwin-Austen, and that these hills 

 in Ehaetic and Liassic times interposed a barrier, which, to a great 

 extent, modified the physical features of the whole line of country, 

 from Frome through a great part of South Wales, and shut out the 

 Secondary deposits from the Coal-basin, within which unconforma- 

 bility very generally prevails, and that the Secondary beds are very 

 insignificant when compared with their equivalent deposits beyond.^ 



J. M. 



> Geol. Journ. vol. xxiii. p. 476. » Geol. Journ. vol. xxiii. p. 537. 



