1844.] 



489 



the latter. The umber is of frequent occurrence, in connection with 

 the pipes in the chalk, botli in Kent and Norfolk. In the former 

 county I have found pipes 6 inches in diameter, and 2 feet in 

 depth, nearly filled with this substance ; and I have frequently 

 observed it mixed with the clay which lies between the chalk and 

 the overlying loam, and which also forms the lining to the pipes. 

 In Norfolk it enters largely into the composition of the pan, and 

 occurs as well in the pipes as in the furrows ; but I have nowhere 

 met with it so pure, nor in such large masses, as in the lower part 

 of the furrow G m, above described. 



The reconstructed chalk, which, in the line of section N O, lay 

 within the furrows at the depth of 3 or 4 feet below the surface of 

 the solid chalk, comjoletely fills u]) and overtops the furrows and 

 the ridge of solid chalk which divides them, on the line of section 

 A G. Over this layer of reconstructed chalk, extending continuously 

 from furrow to furrow, lies a bed of sand. 



The following figure (5.) is a vertical section, passing north 



Fia;. 5. Thorpe Chalk Pit. 



6 <-.-i-' •-_ - 



1. The solid chalk. 



2. The bottom of the furrow A B, filled with sand, umber, and yellow ochre, 



and occasionally containing thin layers of chalk. 



3. Layer of re-constructed chalk. 



4. Sand. 



5. S' General surface of the solid chalk, at the sides of the furrow. 



5. Sand, alternating, in the lower part, with seams of clay and gravel. From 



S, S' to the top of 5, the height is about five yards. 



6. Loam, sand, and gravel. From the bottom of 6 to the surface is about 



eighteen yards. 

 L. The sand-pipe, so marked in the ground-plan, fig. T. 



and south along the middle of the furrow ab. It shows the con- 

 nection of that furrow with the pipe l, and the manner in 

 which the lower strata of crag bend down into the broader and 

 deeper pipes, such as L appears to be. Since the disturbance of 

 the strata does not extend more than 15 feet above the general 

 level of the surface of the solid chalk, the upper horizontal strata 

 of loam, sand, and gravel, of the aggregate thickness of about 



o o 2 



