1847.] LYCETT ON THE OOLITE OF MINCHINHAMPTON. 187 
the workmen; the lowest two or three inches are frequently 
blue. 
Of the Fuller’s earth which underlies the last stratum a brief notice 
will suffice ; its thickness in this neighbourhood varies from 60 to 80 
feet. Northwards in the parish of Bisley, somewhat beyond the limits 
of this sketch, it rapidly thins out, and at Throughham and Lypiatt, 
where the Stonesfield slate in mass begins to occupy its position, 
the thickness is reduced to about 9 or 10 feet. It consists of strati- 
fied blue and brown marls and clays, traversed by three or four bands 
of hard brown argillaceous rock called “clay rag.’ The uppermost 
of these is a lamellar argillaceous slate having all the characters of 
the Stonesfield slate, and judging from the number of places where it 
occurs, would appear to be continuous over the whole district. Oc- 
casional traces of various organic remains may be observed, but rarely 
sufficiently distinct to be recognised. The shells distributed through 
the Fuller’s earth, though abundant in certain layers, belong to few 
species ; Terebratulee predominate. One or two bands of stone and 
the neighbouring clays are nearly made up of the valves of Ostrea 
acuminata. 
The soil over the Fuller’s earth is the best in the neighbourhood ; 
and when properly drained constitutes good pasturage and orchard 
land. The springs which burst out at the base of the superincum- 
bent oolite frequently afford the means of ministering to domestic 
purposes ; accordingly its course may usually be traced in populous 
districts by a zone of cottages and gardens girdling the hill-sides, and 
affording a strong contrast to the barren slope of the inferior oolite 
beneath. 
From the occurrence of a series of clay beds between two rock for- 
mations ina single hill-slope, it may be conjectured that landslips are 
of frequent occurrence, and accordingly we sometimes find the steep 
slope of inferior oolite rendered fertile by a coating of the marls of the 
Fuller’s earth. 
In illustration of the diversity of mineral characters which may 
exist in the great oolite within a small area, I will mention that at 
the Box, one mile from the large section which I have quoted, the 
beds A, B and C are absent, and their place is occupied by a thick 
stratified deposit of brown clay containing several bands of argilla- 
ceous rock and nodules ; in fact, a repetition of the Fuller’s earth as 
far as mineral character is concerned. From this uncertainty it fol- 
lows that the success of opening and working a quarry in this forma- 
tion somewhat resembles the risk of a mining speculation ; a slight 
accidental circumstance will sometimes defeat the project by rendering 
the quarryman unable to compete with others more favourably situ- 
ated. 
Authorities referred to in the following List. 
ENSASSIZ, | ocnic tasers Description des Echinodermes de la Suisse, 4to. 
Broun ............. Lethaea Geognostica, H. G. Bronn. 
