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 cen- 

 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 

 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 



