GEOLOGY 
yielding, besides aquatic forms of life, remains of land plants and 
animals. It varies much in thickness within short distances, and in 
fact is not a persistent bed, sometimes occurring only in ‘ pockets’ or 
‘pipes’ let down into the underlying strata. The Series is a richly 
fossiliferous one in some places, but not here, and it represents in time 
the Stonesfield Slate of the south of England, from which have been 
obtained many fine fossils that adorn the walls of our museums. 
While estuarine and freshwater conditions continued in the north, 
marine conditions set in from Lincolnshire southwards, commencing 
with the deposition of oolitic limestone. This does not indicate a 
deep sea, for the limestone was in all probability the detritus of coral 
reefs, which are built up in shallow water on a slowly-sinking sea-bed. 
The influx of the sea must have been from the south, and the warm 
currents thus brought in would be favourable to the growth of corals. 
The Great Oolite here consists of two divisions which are not very dis- 
tinct from each other—the Great Oolite Limestone and the Great 
Oolite Clay. The former is by far the most persistent, extending 
through the midland and southern counties, while the latter is repre- 
sented in the south of England by the Forest Marble, a shallow-water 
and perhaps partly estuarine deposit which gradually takes its place. 
The Great Oo.tte Limestone is quarried for lime-burning and for 
use as a building-stone at several places near Bedford, where its thick- 
ness varies from 25 to 32 feet. It extends from Kempston south of 
Bedford westwards to Cold Brayfield, Carlton, and Harrold, and north- 
wards to Puddington and Farndish. It usually consists of pale grey, 
dark blue, and bluish-grey limestone, either earthy, oolitic, or flaggy, in 
beds of varying thickness (from 1 foot to 10 feet) separated by thinner 
beds of pale grey, dark blue, or mottled clay or clayey marl, both lime- 
stone and clay frequently being crowded with specimens of Ostrea 
sowerbyi, The limestone is occasionally false-bedded or current-bedded, 
which indicates shallow-water deposition, this inference being confirmed 
by the great variations in the thickness and character of the beds which 
take place within short distances. After O. sowerbyi the next most fre- 
quent fossil is O. subrugulosa. Myade are abundant, and remains of 
saurians and fishes also frequently occur. 
The water-supply of Bedford is derived from this formation. The 
water has been analysed, with that from the River Ouse adjacent to the 
pumping-station, by Professor. Attfield, F.R.S." Both waters are hard, 
but the well-water is about twice as hard as the river-water. 
The Great Oouire Cray is very variable in colour, calcareous in 
places, contains selenite, and has at or near its base a nodular ironstone 
band about which the clay is sometimes dark and carbonaceous. It 
occurs near Bedford but is not persistent ; the Cornbrash, at West End, 
Stevington, resting directly on bluish oolitic limestone. It is only a 
few feet in thickness. 
1 See Trans. Herts Nat. Hist. Soc. iv. xxviii.—xxix (1888). 
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