1844.] 



487 



lines of section, the furrows are excavated in solid chalk, and 

 they are separated from one another by an intervening ridge of 

 solid undisturbed chalk. 



Fig. 3. Thorpe Chalk Pit. 



( Cross Section of the bottom of the furrow G M. ) 



W. E. 



1 . Solid chalk. 



o. Yellow ochre, 



s. Sand. 



c. Chalk. 



M. Sand mixed with umber. 



3. Layer of reconstructed chalk. 



On the line of section n o, each of the furrows is from 7 to 8 



feet deep, and, at the surface of the solid chalk, is about 4 feet 



wide ; but on the line of section A G, both the furrows are wider 



' and shallower. At and near the line of section n o, the width of 



the furrows on a level with the surface of the solid chalk, is some- 



j times less than it is about a foot and a half below that level ; but 



I at a greater depth the width again diminishes, and it then tapers 



j downwards to the bottom. Sometimes, however, the transverse 



section is nearly that of a wedge. 

 j Near the line of section n o, the lower part of the furrow G M, 

 to the height of about a foot from the bottom, was irregular in 

 I shape, and, at that height, was from H to 2 feet wide. This part 

 was sometimes filled with a mixture of yellow ochre and umber, of 

 i a blackish or bi'own colour, and very low specific gravity : some- 

 times the umber lay above and the ochre below, a thin layer of 

 fine sand separating the two ; sometimes a layer of fine ferruginous 

 I sand lay beneath the ochre and umber, and sometimes, as in Fig. 

 I 3., thin irregular layers of chalk were mixed with the other 

 I contents of this lower part of the furrow. At the bottom of the 

 j furrow A B, near the point A in the ground plan, was an accumu- 

 I lation of water-worn pebbles, which was covered by sand. (See 

 I Fig. 4.) 



' VOL. IV. PART III. O O 



