part 1] SAXDS A^D GKAYELS AT LITTLE HEATH. 39 



thin tabular flints, numerous Reading pebbles with the typical 

 nocling, and small angular pieces of broken flints, the latter usually 

 having a green surface-colouring, probably glauconitic. Also a 

 small number of quite small, smooth, well-rounded, and, occasion- 

 ally, polished pebbles, and pieces of ferruginous concretions. 

 There are also many fragments of Inoceramus washed out of the 

 Chalk, in which the fibrous structure is still retained, but the car- 

 bonate of lime has disappeared and has been replaced by silica and 

 apparently some iron-oxide. These fragments of Inoceramiis are 

 indeed found both in the gravel and in the loamy sand above. 

 Most of the thin flints lie with their long axes parallel to the 

 irregular Chalk surface beneath, and thus give a bedded aspect to 

 the clay, which, indeed, seems to be somewhat laminated. 



This deposit rests on the crest of a knob of the Chalk, but on the 

 sloping sides of the Chalk a thin la\ T er of fine sand sometimes 

 intervenes, part of which is white, but mostly red. When the 

 clay is disintegrated it is also found to contain a good deal of sand, 

 a large percentage of the grains of which are stained black. 



The feature of the dark clay is its close resemblance to the bed 

 with large unworn flints that over a wide area occurs at the base of 

 the Eocene deposits, whether these be Reading or Thanet, which 

 rest directly upon the Chalk. This Eocene bed is often known as 

 the ' Bullhead,' and it will save useless multiplication of terms if 

 this name is adopted in the present instance. 



So far, no contemporaneous fossils have been found in the Little- 

 Heath deposit, but the extent of the exposure which could be 

 examined was extremely small. 



A somewhat similar deposit is found at another exposure of the 

 Chalk, which has been excavated at the bottom of an old pit, about 

 100 yards away to the north-west. This is at a slightly lower 

 altitude, and the pebble-beds here were thinner than in the pit 

 under description. 



Gekeeal Notes. 



It is an important feature in these beds that in the Berkhamsted 

 area they are always found resting directly upon the Chalk. In 

 this respect they differ from all kindred deposits hitherto found 

 north of the Thames, which (where the basal junction has been 

 reached), invariably rest upon the Eocene beds. 



Mr. W. Humphrey gives the following further information : — 



' The gravel is usually in potholes of the Chalk, though it is often found at 

 the surface lying quite horizontally. It sometimes reaches nearly 30 feet in 

 thickness.' 



Each pit has what he calls a ' water-course ' at the bottom, 

 which acts as an outlet of the water into the Chalk ; and he has; 

 sometimes come upon a cavity as big as a wheelbarrow, from which 

 the Chalk has been dissolved. He has never met with a single 

 patch of the brick-earth (altered Reading drift) in any part of 

 Little Heath Common. 



