46 
LENHAM BEDS. 
With the large unworn flints we have at present nothing to do. 
As a rule they are only the 'insoluble residue left during the 
formation of the pipes, or let down from the superflcial clay-with- 
flints. It is probable that a good deal of the clay also belongs to 
this category. 
Turning now to the sand and ferruginous sandstone, the material 
does not at first sight look very promising—to a superficial 
examination it is nothing but a rusty sand of somewhat finer 
grain than is usually found in the Drift. However, the sand in 
some of the pipes shows a greenish tinge, and if a number of the 
larger blocks of ironstone be broken up, one or two of them will 
probably yield traces of the material in something more nearly 
approaching to its original state. The sand is then loose and 
very glauconitic, though even in the least altered specimens it is 
still somewhat rusty and has been entirely decalcified. 
Keturning to Lenham on a second visit, after studying the 
Pliocene beds at Antwerp, I was much struck with the simi¬ 
larity of the deposits. We find the same fine sand full of 
glauconite,* and also the same tendency to oxidize into masses of 
ironstone with casts of fossils, like those which M. Van den Broeck 
had shown me near Diest. 
In the pit just described the depth to which the material has 
subsided through the pipes is so great-—probably not less than 
80 feet—as quite to obliterate any trace of the order of succession. 
However, a certain number of the blocks of ironstone evidently 
belong to the bed that rested directly on the Chalk, for besides the 
Pliocene fossils they contain unworn flints and derivative frag¬ 
ments of Inoceramus and spines of Cidaris clavigera. Of 
derivative Eocene fossils not a trace has yet been observed, 
though the scattered pebbles of flint may possibly be a relic of 
one of the older pebble beds. Small pebbles of quartz are also 
occasionally found. 
This pit is not quite at the highest point on the Lenham Downs, 
though very near it, A search scon showed, however, that the 
same fossiliferous ironstones cap the highest part of the hill, for 
a cast of Terebratula grandis was found in a pipe in the road¬ 
cutting near Lee Farm, a quarter of a mile to the north-west. 
This was at a height of about 620 feet, 680 feet being the highest 
point within several miles. About 60 yards higher up the road 
•bright red or mottled loamy micaceous clay is exposed by the road¬ 
side, but it is thin and is immediately hidden by the clay-with-flints. 
Similar red clay is seen in the road north-north-west of Lee Farm 
at about the same level. 
Unfortunately there are so few pits away from the escarpment, 
and the dip slope is so obscured by clay-with-flints, that little 
can be said about the succession or nature of the deposits where 
undisturbed. 
A quarter of a mile west-north-west of Marlow Farm there is 
another exposure, placed a short distance down the escarpment 
* Glauconite is a silicate of ferric oxide, potash, and alumina, but varies much 
in composition and specific gravity, and is probably always mixed with impurities. 
