Geology. 227 



they measure about 30 ft. Though but rarely exposed, they 

 are persistent round our hills ; yet at Wellow, a short dis- 

 tance beyond Midford, they thin out, and the Inferior Oolite 

 limestones rest immediately upon the Lias, {pide " Froc." 

 Bath Nat. Hist, and A. Field Club, vol. Hi., p. 133.) 



Directly overlying the Sands is a peculiar con- 

 inferior Oolite. . 1 1 1 , .- 



glomeratic or nodular bed, from 18 in. to i 

 ft. thick, very fossiliferous, containing the characteristic 

 shells of the Inferior Oolite — e.g., Rhyncondla spinosa, 

 Trigonia costata, Astarte excdvafa, Ammonites Brochii, 

 etc., succeeded by other limestone beds of the same 

 group, averaging about four feet in thickness in the par- 

 ticular section before-mentioned, eastwards of the tunnel, 

 under Devonshire-buildings. We, however, seek in vain 

 for that great development which is found in the Chelten- 

 ham district, where the Freestone beds, affording the prin- 

 cipal building stone, alone measure some 100 ft. The 

 Trigonia bed ; Gryphxea bed ; Ragstones ; Flaggy Free- 

 stone ; Fimbria bed , Freestone and Ferruginous Peagrit, 

 measuring more than 200 ft. together, are here in our 

 district comprised in, at the most, 50 or 60 ft. ; sometimes 

 much less, as at the well-known section at Vallis (De la 

 .JBeche, "Mem. Geol. Survey, vol. i., p. 288), where thin 

 beds, a few feet thick, rest upon the planed down up- 

 turned edges of the Carboniferous Limestone. Mr. H. B. 

 Woodward divides the beds into : — 



ft. 



1. Soft Freestone, more or less oolitic ... 40 to 50 



2. Rubbly stone, consisting principally of corals 10 



3. Hard brown limestone, abounding with casts 



of shells ... ... ... 6 



The Inferior Oolite follows the course of the Avon on both 

 16* 



