19 
CORAL RAG and PISOLITE. 
Soil.— C olour, Dark brown. 
Consistence , Loose when dry ; rather tenacious orkneadable when wet; thickly strewed 
with small stones, roundish or irregularly shaped, which in roads wear 
white. 
Subsoil. — Moist Clay and a rough irregular Limestone. 
Excavations, Shallow, on outcrop of the rock; stone whitish; where mixed with Clay, hold 
water ; where sandy, dry. 
Stratum, Lightish blue in deep pits ; where the Stratum is entire, beneath its incumbent Clay 
hard and solid, except the cavities occasioned by stems of Madrepores. 
The Pisolite part of the rock beneath has a dryer, stony, and less adhesive soil, 
of the sort usually called Stonebrash. The stone in some of its beds is white, 
and composed of unequal sized ova. Loose ova may be seen at the sides of banks 
and other bare places. 
Water, flows in abundance from this rock, and the Sand and Sandstone, which is the 
bottom of the Stratum. 
My Geological Table of organized Fossils shows that this rock and the Sands have been repre- 
sented on my map by the same colour ; but now, by the better arrangement of my fossils in the 
British Museum, and my subsequent observations, these Strata are more distinctly divided 
The Coral Rag consists chiefly of lumps of coralline Limestone, which in the quarry are very 
rough, irregular, and dirty ; but where roads cross the outcrop, or where this stone is used as a 
road material, it wears to a smooth surface, which is whiter and harder than any other stone in 
the vicinity. 
The Pisolite Freestone beneath is softer. In some parts it being an Oolite of fine grain, 
is used in building, and in specimens without organized Fossils, is scarcely to be distinguished 
from Portland Stone. 5 
Coral Rag and Pisolite, with the Sand and Sandstone beneath, make a surface of dry land 
which, within a generally moist surface of Clay land, is very desirable for tillage, and is com^ 
monly thus appropriated. 
Among the stones turned up by the plough, most of its organized Fossils may be found, but 
the quarries generally produce sharper and better specimens. 
The greatest breadth of surface formed by the outcrop of this Stratum is in Wiltshire, Berk- 
shire, and Oxfordshire : its course north-eastward becomes obscure, or is covered with "alluvia! 
matter before it reaches Buckinghamshire. ‘ 
From Steeple Ashton, Wiltshire, the south-western course is indistinct, or the stone is deeply 
covered in the high hills of Sand, and forms part of their altitude ; as in this direction it re-ap- 
pears in the low part of Longleat park ; and beyond the high Sand hills of Stourton, the 
