SOILS : GREAT OOLITE SERIES. 469 
The uplands of Forest Marble north and north-east of Cirencester, form 
flat monotonous tracts of chiefly ploughed land, -with stone walls, and few 
trees. Much of the subsoil is a tenacious clay of variable thickness 
intermingled with the " flat stones." 
Great Oolite Clay. 
In reference to the Great Oolite Clay, Prof. Judd remarks that " The 
beds of this formation give rise to a cold and wet soil, very similar in 
character to that of the lower beds of the Upper Estuarine Series. For- 
tunately, however, they do not occupy any considerable areas in the 
district, but form only the short slopes between the Cornbrash and Great 
Oolite limestones ; and even in these, the unkindly nature of the soil is 
usually somewhat tempered by the downwash from the overlying strata. 
Some of the tracts based on this division of the series have only recently 
been brought under drainage and cultivation."* 
Cornbrash. 
The Cornbrash forms a reddish-brown and stony or " brashy " soil, the 
stones being embedded in loam of a rather tenacious character when wet. 
As remarked by William Smith " it is kept loose enough for cultivation 
by the small rubble stones thickly strewed 011 the surface of its ploughed 
fields, but which disappear when laid down to pasture."f In many fields 
fossils may be picked up, especially Pholadomya, Myacites, Gresslya, &c. 
The fields are usually divided by hedgerows. The rock outcrops in a 
gentle feature above the Forest Marble clays, and dips beneath the low 
ground formed of Oxford Clay. The quarries are seldom deep, but opened 
over considerable areas in the fields. Smith observed that after the stone 
has been stripped off, and the pits " well levelled, resoiled, and drained," 
the land may be rather improved than injured. On the other hand H. W. 
Bristow informed me, that in a field south of Sherborne, where there was 
formerly a Cornbrash soil and good land, the farmer by degrees had all 
the stones removed, and then complained that the field was not so fertile 
the fact was, there was but a thin layer of rubbly Cornbrash on the clays 
of the Forest Marble. 
In the south-west of England corn and sometimes beans and turnips 
are cultivated. The name " Cornbrash " was applied in Wiltshire in 
distinction from the " Stonebrash " of the Great and Inferior Oolites. 
An analysis of Cornbrash by Prof. A. Voelcker, showed '177 of phos- 
phoric acid and '241 per cent, of sulphate of lime, and their presence, 
according to Prof. Buckman, contributes to the fertility of the Corn- 
brash soil.J 
In Northamptonshire, as remarked by Prof. Judd, the soil formed by the 
Cornbrash has usually a reddish hue like that of the Lincolnshire Lime- 
stone, while that of the Great Oolite has more commonly a black tint. 
Locally the name " Eedbacks " has been applied to the rubbly rock. In 
the midland counties the Cornbrash "does not enjoy the reputation among 
agriculturists which it has in the south of England." 
* Geol. Rutland, p. 218. 
f Strata Identified by Organized Fossils, 1816, p. 25, 
j Quart. Journ. Geol. Soc., vol. xiv. p. 120 ; Ann. Nat. Hist., ser. 2, vol. xii. 
p. 325, and Proc. Cottesw. Club, vol. i. p. 262. 
Geol. Eutland, p. 219. 
