File:The Quarterly journal of the Geological Society of London (13365490143).jpg

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others spherical ; many were entire, whilst others were broken, and
glittering with yellow and brown crystals of calcareous spar, with
which all the interstices of the septaria were lined or filled. Some
of these masses were hollowed out by the action of the waves into
regular basins, which at low-tide stand up from the sands full of
water, and are three or four feet deep, forming excellent foot-baths
for the weary pedestrian.
" Many of these septaria struck me as curious from the zone or belt
of cone-in-cone clay with which they were encircled, as in the sub-
joined sketch (fig. 6), which represents the usual form and appear-
ance of one of these zoned nodules.
Fig. 6. — Septarium with a zone of Cone-in-cone Clay,
Fig. 7. — Section of a Septarium, from Onekakara,
a, a. Spherical body of the
Septarium.
b. Fragment of bone imbed-
ded in the Septarium.
" Fig. 7 is a section of the same, exhibiting the cone-like structure.
The direction of the apices of the cones is towards the centre of the
nodule ; the coating of the other part of the sphere (fig. 6, a, a) is
composed of clay with crystals of selenite ; the cones are represented
disproportionately large, to render the structure intelligible. These
septaria, with the exception of the belt of cone-in-cone clay, are so
like those I recollect seeing extracted from the London clay off the
coast of Sussex, and used for Roman cement, that I think they may
be applicable to the same economical purpose. I gave some to Capt.
CoUinson, R.E., who had it burnt and ground by a mason, who pro-
nounced it worthless ; but I still put faith in my cement, and not
in the lime-burner*.

• A portion of one of these nodules has, through the kindness of Sir Henry De