15 
PORTLAND STONE. 
Sim,.—- Colour 9 Brown. 
Consistence , absorbent, sandy loam ; much intermixed with stones, which vary in 
quantity, size, and hardness, as the different beds of rock occupy the 
surface, commonly called Stonebrash. 
Subsoil, Orange brown, all stone, or sand and stone alternating, absorbent. 
Excavations, all dry ; in sand and stone ; some made down to the water. 
Stratum, masses of stone in thick beds or layers ; bluish white, brownish white, and some 
hard blue or blue grey. 
Disintegration , Few persons who have not made observations on this subject can be 
aware, how a rock nearer and nearer to the surface, gradually divides 
into building stone, wall stone, rubble stone, and soil. This should 
be particularly attended to in tracing the terminations or outcrops of 
rocky Strata. 
Water.— -Copious springs flow from the bottom of the rock. 
The Swindon stone, unlike many other great rocks, forms not of itself, any elevated or 
distinct ranges of hills, except at particular places, and then only, too frequently in conjunction 
with the lower Strata, by which those of the stone are hidden or much obscured. The rock is 
also subject to great change in appearance and quality, yet the Portland stone can be easily 
identified at particular places, along the course of the Stratum which produces it, to as great an 
extent as some of the other Strata with which it alternates. Portland Isle is one extremity, and 
Hambledon hills, in Yorkshire, the other. The rock, however, it is evident from various 
causes, cannot, in a connected line of outcrop, ever be traced from one of these points to the 
other, which is a space of 300 miles, but the Strata above and below, which seem to inclose the 
rock, if not the identical beds of stone, may he recognized for a considerable part of the distance. 
It is best known in Portland, Purheck, Wiltshire, the vale of Aylesbury, and in Kent and the 
vale of Pickering. Hambledon hills also produce the Portland variety. The stony land on the 
western border of Dorsetshire, appears to be the same. It has long been worked for buildi ng, 
equal in quality to that of the noted island, in the vale of Wardour. Sand is much blended with 
it at Swindon. 
This rock, though long worked to a great extent in several places, in others would be disco- 
vered with difficulty. Its site is in many parts near the foot of the Chalk hills, and in others so 
widely distant from them as to leave the intermediate course doubtful with a skilful Geologist. 
It contains some very thin beds of chert or flint, and some thick beds of Freestone, us soft as 
Chalk. 
Large flinty nodules are sometimes enclosed in the Freestone, the beds of which vary much in 
different quarries. The organized fossils vary less. They are therefore in this instance, 
remarkably useful in identifying the Strata. 
