'\^> '^f^'the London and Hamijshirc Basins. 



285 



nriThe first and uppermost we may call the Tertiary Zone. The 

 beds and sprinklings of this division consist mainly of shingle of 

 the eocene sera, with some angular flints and sandy or argilla- 

 ceous loam, abounding everywhere with rounded pebbles. 



The next, the Cretaceous Zone, consisting entirely of angular 

 or unbroken flints, in which we very rarely find a pebble except 

 when entangled in a more than usual invasion of the clays of 

 the lowest tertiary formations. . ,i 



The Subcretaceous, which consists of angular flints with a large 

 admixture of the ironstone, sandstone, and chert of the green- 

 sand beds. 



And fourthly, the Wealden Zone, in which the flints, except in 

 a few points on the margin of this formation, have disappeared 

 along with the pebbles and other materials characteristic of the 

 strata higher in the order of geological superposition. It will 

 be convenient, perhaps, to put this in a tabular form : — 



Pebbles and broken shingle 



1. Tertiary zone. 



2. Cretaceous zone. < 



Drift. < 



4. Wealden zone. 



fxiia{«?( , rr^ .' bcds ; slight admixture of 



angular flints; sandandloam, 

 and some chalk -rubble. 

 Angular flints. Pebbles very 

 rare. Very little loam, but 

 sometimes much chalk- 

 rubble. 



r Angular flint with chert, iron- 

 3. Subcretaceous zone. < stone and sandstone, much 



1^ sand and little loam. 



rlron-rag (a conglomerate of the 



I debris of the various beds 

 above and below the Weald 

 clay) . Beds of diluvial loam^ 

 sometimes of great depth. 



Of these, the two first contain the bones of mammals, and the 

 usual organic remains of what is called the Pleistocene. In the 

 third, these are very rare ; and in the fourth there are none 

 at all. 



All the mineral substances of these several zones belong to 

 the strata which are found in and around the great anticlinal 

 line, if it be determined that the " grey wethers ^' are the pro- 

 duction of any of the tertiary beds. And no substances foreign 

 to these strata are to be found in the drifts ; unless it be that 

 some intrusions from the older beds west of the area in review 

 may by accident be found in that part of the line ; of which, 

 whether or no, I am not critically certain. 



Moreover, if by pleistocene is meant a marine deposit made in 



Phil Mag, S. 4. Vol. 2. No. 11, Oct, 1851. X 



