122 British Association for the Advancement of Science. 
Mr Lyell read a paper on the Tubular cavities filled with gravel 
and sand in the Chalk near Norwich. 'The chalk near Norwich 
is covered with gravel, sand and loam, of variable thickness, 
much stained with iron, occasional masses of ferruginous sand- 
stone being interstratified, in which are casts of the shells of the 
Norwich crag. The shelly crag itself forms here and there part 
of the same deposit. The outline of the chalk, at its junction 
with the incumbent gravel, is very irregular. In some places, 
tubular hollows, having the form of inverted cones, and filled 
with gravel and sand, are prolonged downwards to variousd epths 
into the chalk. These cavities vary in width from a few inches 
to 8 yards and upwards, and in depth from a few feet to more 
than 60 yards. Some are tortuous, but most of those at Eaton, 
two miles west of Norwich, are perpendicular. The materials 
filling the pipes agree precisely with those covering the chalk, 
with the exception that in the pipes they are unstratified. The 
pebbles in the gravel consist of rounded flint and quartz ; but no 
shells or pieces of chalk, or any calcareous substance, occur in 
the pipes. In general, coarse sand and pebbles occupy the cel- 
tral parts of each pipe, while the bottom and sides are lined with 
a fine ferruginous clay, which however is permeable by water. 
This clay contains no calcareous matter. ‘The chalk, for the 
distance of several inches, or even sometimes four or five feet 
from its junction with the sand pipe, is in a moist and softened 
slate, and contains a slight mixture of fine sand and clay, by 
which it is somewhat discolored. The chalk, at points more 
remote from the tubes, is white, pure, and perfectly soluble in 
acids. The pipes, which do not exceed a foot and a half in di- 
ameter, are often crossed by horizontal layers of flint nodules, 
which have remained in situ, while their chalky matrix has been 
removed. From this circumstance, the author infers that the 
pipes were due to the corroding action of water containing acid, 
which could not dissolve flint. But it is clear that the tubes 
were not first excavated to their present width and depth, and 
Sy 
then filled subsequently and at once with gravel, for in that _ 
case the siliceous nodules would have been found in a heap at 
the bottom of each large cavity, having been derived from all 
the intersected layers of flint. This never happens, the larger 
flints being invariably dispersed irregularly through the gravel 
and sand which fills the tubes. Mr. L. therefore inferred that 
* 
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