486 DR. HENRY WOODWARD ON EAST ANGLIAN GEOLOGY. 
contain over 21 per cent, of silica, so that it is now generally 
concluded that the flint has segregated out of the Chalk and 
formed into concretionary nodules, much in the same way as iron- 
pyrites forms into nodules or concretions in the Gray Chalk and 
the Gault-clay, and in which “ Septaria ” (which are nothing more 
than concretions) are formed in layers in the London Clay. 
Large pear-shaped or cylindrical flints of great size, with a cavity 
through the centre (called by Dr. Buckland “ Paramoudra,” 
a name given to similar large flints in the Chalk of Antrim and 
Co. Down, Ireland), occur singly in many localities in the Chalk 
and in some places forming more or less regular columns, the pot- 
stones resting one upon another as in the Chalk at Trowse and 
Whitlingham, and at Ilorstead on the river Bure in Norfolk. 
They are no doubt due originally to the dissolving up and the 
redeposition of the siliceous spicules of Chalk sponges which must 
have flourished to an enormous extent in the sea of the Chalk- 
period, as their remains are very numerous in some beds, although 
the spicules of flint are often destroyed or converted into an almost 
amorphous mass of flint. From the nature of the materials form- 
ing the Chalk, as well as the organic remains which occur in it, the 
Chalk is considered to have been formed in a deep and open sea ; 
indeed recent researches carried on in the North Atlantic Ocean 
show that material for a continuous calcareous deposit with flint- 
nodules is now being deposited at depths of from 400 to 2,000 
fathoms, while many forms of microscopic animal life such as 
Globigerina, and Coccoliths and Coccospheres occur in equal 
abundance in both the modern marine deposit and the ancient Chalk. 
What does the Chalk rest upon? 
Coal-boring in the Eastern Counties. 
I have said that the oldest formation cropping out at the 
surface in East Anglia is the Cretaceous, this term including the 
“Bed Chalk” of Hunstanton, the “Carstone” of West Norfolk, 
the Cambridge Greensand, and the Gault-clay. Until 1854, when 
the Harwich w r ell-boring was carried to a depth of 1098 feet, the 
base of the Chalk had never been reached in this neighbourhood, 
although 500 well-borings have been made within the last twenty 
years. 
