THE PORTLAND BUILDING STONE. 
207 
though they cannot be said to die out. Numerous quarries are 
opened in them along a range of country about six miles broad, 
which extends from a little north of Aylesbury to a line 
between Brill and Thame. The best quarries are on the road 
between the latter town and Aylesbury ; those at Stone having 
been worked over two hundred years, and many good build- 
ings erected from them. There are two main blocks, the upper 
a softer and more uniform stone, and the lower hard, irregular, 
and fossiliferous, with a bed full of Trigonias at its base. 
In the neighbourhood of Brill a particular bed, perhaps even 
lower in the series, is a rather more sandy limestone of darker 
colour, known as the i greys/ None of these are oolitic, or 
of such super- excellent quality as would ever draw general 
attention to them. Though of no great thickness or impor- 
tance, they are the only representatives of the Portland Stone 
in this district, for immediately above lie thin-bedded, white, 
I freshwater limestones usually assigned to the Purbeck series. 
It is interesting to see the rapid change from one condition 
to the other without any mark of disturbance, and difficult to 
conceive the exact set of circumstances that should have rendered 
it possible ; yet occasionally one does get a glimpse of the 
intervening conditions, as when in a quarry is seen a great 
rounded excavation, in shape like the section of a river, filled 
with the mud of Purbeck times, and then buried and preserved 
by overlying deposits. In such a case one sees the very river 
which emptied itself elsewhere into the lake where cyprids 
abounded, pond-snails flourished, and insects dying dropped 
their tiny wings. In places, too, we even find the boundary 
of the area of deposit, or at least its neighbourhood, where all 
things seem reduced to a minimum, and formations elsewhere 
important lie in a few feet. Thus in a quarry at Long Crendon 
may be seen in not more than eight feet four formations. 
Below is the Portland Stone, here worked for rough building 
material, then a foot or two of Purbeck-limestone beds broken 
at the top, then the ferruginous beds of the Lower Greensand, 
and over all about two feet of Gault with characteristic fossils ! 
No wonder in such a neighbourhood the Portland rock should 
be somewhat deficient. 
The worked stone of Oxfordshire is but a continuation of 
the same bed in Bucks, and is of no great value. Nevertheless, 
at Great Hazeley are beds which have long been worked, and 
are of a more solid quality ; at the base, and also above the best 
block, is a bed full of the characteristic Trigonias. 
The next district in which Portland Stone is worked is near 
Swindon, in north Wiltshire. The same beds which we have 
already seen yielding an inferior kind of stone are worked for 
local purposes in small quarries in the neighbourhood of that 
