fuller's earth. 295 



Rollwriglit (or Rollerich) stones, near Little Rollvvright, not far from Chipping 

 Norton, are formed of Inferior Oolite. ' 



Analysis of the Inferior Oolite shows about 90 per cent, of carbonate of lime, with 

 small portions of silica, alumina, etc. 



The soil is reddish-brown and brashy ; the character of the ground is hilly, and 

 sometimes comparatively barren. The higher grounds, especially on the Cottes- 

 wold Hills, are largely devoted to sheep-walks ; but where the soil is deep, it is 

 fertile, and forms good corn land. 



FULLER'S EAETH. 



The term Fuller's Earth was applied geologically by William 

 Smith, in 1816, to a thick deposit of grey clay and marl, with 

 occasional nodules of earthy limestone ; this is divided near the 

 middle, in some localities, by beds of soft argillaceous limestone, 

 called the Fuller's Earth Rock. The formation is characterized by 

 the presence (south of Bath) of beds of blue and yellow Fuller's 

 Earth, a marly clay, which is of a brown or yellowish colour near 

 the surface, and blue deeper down. As described by Mr. Bristow, 

 this Fuller's Earth is of commercial value, has a greasy feel, and an 

 earthy fracture ; it yields to the nail, and affords a shining streak ; 

 it scarcely adheres to the tongue; becomes translucent when placed 

 in water, and falls into a pulpy impalpable powder, without forming 

 a paste with it.- 



The maximum thickness of the Fuller's Earth formation may 

 be as much as 400 feet. It rests conformably on the Inferior 

 Oolite, and is overlaid by the Great Oolite or Forest INIarble. 

 The Fuller's Earth Rock is from 20 to 30 feet in thickness, and 

 may be described as a blue marly limestone weathering pale-grey 

 or yellowish-grey. According to Mr. Bristow it is feebly developed 

 in the neighbourhood of Bath, but becomes of importance between 

 Kilmersdon in Somerset and Beer Hackett and Thornford, in 

 Dorset. 



The Fuller's Earth is characterized by Osfrea acuminata, Tere- 

 hratida ( Waldheimia) ornithoccphala, and Rhyjichonclla varians {niedia). 



Among other fossils may be mentioned Aiiunoniles subcontractus 

 {inodiolaris of Wm. Smith), A. maovcephahis, Bcletnnitcs paralldiis, 

 Ostrea Soiverbyi, Pcctcn vaga7is, Pholadomya iruncata, P. ddloidca, 

 Goniomya anguli/era, G. literata, Homomya gibbosa, Isocardia con- 

 centrica, Ceromya plicata, Lima duplica/a, Placunopsis socialis, Modiola 

 Sowerbyana, M. gibbosa, Terebratida globata, T. pcrovalis and Seipiila 

 tetragona? Glyphea has been met with, and many species of 

 Entomostraca and Foraminifera have also been obtained.* Some 



^ P. Geol. Assoc, v. 179. 

 ^ Glossary of Mineralogy, 1 85 1. 



3 See PhiUips, Geol. Oxford, etc., p. 166; W. Smith, Strata Identified, 1816; 

 E. Witchell, Geol. Stroud, p. 69. 

 * T. R. Jones and C, D. Sherborn, G. Mag. 18S6, p. 272. 



