and Sand called " Sand-pipes," in the Chalk near Noi-^ich. 259 



Eaton is about twenty feet thick. The clay is also similar to 

 the finer portion of that found in the gravel above. As a 

 general rule, admitting of few exceptions, the sand and peb- 

 bles occupy the central parts of the pipe, while the sides and 

 bottom are lined with clay. In the clay, at the bottom of one 

 small pipe, which was only six inches wide at the top and a 

 yard deep, I found some black carbonaceous matter, probably 

 derived from the roots of trees which had penetrated from 

 above. 



Not a particle of calcareous matter, whether organic or 

 inorganic, occurs in any part of the pipes, either in the mid- 

 dle or at the sides, where the clay is in contact with the chalk. 

 Large unrounded nodules of flint, still preserving their ori- 

 ginal form and white coating, {bb) are dispersed singly, and 

 at various depths, in those larger pipes which exceed one foot 

 or one foot and a half in diameter. The smaller pipes, in 

 which diese loose flints never occur, are frequently crossed by 

 horizontal layers of siliceous nodules, as at c, f/, e, fig. 1, which 

 still remain in situ, not having been removed together with 

 the chalk in which they must have been originally imbedded. 

 Single flints, forming part of these continuous layers, some- 

 times appear in the middle of a small pipe, as at d, fig. ], sur- 

 rounded and supported by sand, so that at first sight it is not 

 easy to imagine how it can have retained its position during 

 the substitution of the sand and gravel for the original chalk. 

 But it should be remembered that these flints in the chalk 

 near Norwich, are usually of a large size and irregular shape, 

 and may be still supported at one extremity by the chalky 

 matrix. Neither a loose nodule of flint nor a heap of nodules 

 has ever been observed at the bottom of a sand-pipe at Eaton. 



In general there is no order in the arrangement of the ma- 

 terials of the pipes except that the coarse sand and gravel oc- 

 cupies the middle of each and the clay the outside and bot- 

 tom. There are some exceptions to this rule ; but even where 

 coarse sand and gravel come into immediate contact with the 

 chalk they are usually imbedded in a paste of sandy clay, 

 which is wanting in the centre of the pipe. This parting 

 layer of clay, an inch or more in thickness, which lines the 

 walls and attains some thickness at the bottom, may some- 

 times be traced upwards until it bends round, and continues 

 to intervene between the chalk and overlying gravel, so that 

 the same layer which is perfectly vertical within the pipe be- 

 comes horizontal over the chalk, as at f, fig. 1 . The fine 

 yellow clay at the bottom of some of the pipes has been found 

 by Mr. Colkett, of Norwich, to make a good oil paint of a 

 colour between raw sienna and Roman ochre. 



S2 



