286 
EOCENE PERIOD. 
[Ch. XXI. 
found near Newhaven, and at other points, as will be seen by 
the map. These are now wasting away, and will in time 
disappear, as the sea is constantly encroaching and under- 
mining the subjacent chalk. 
The secondary rocks, depicted on the map, may be divided 
into five groups :— 
1. Chalk and Upper green-sand. — This group is the upper- 
most of the series ; it includes the white chalk, with and 
without flints, and an inferior deposit called, provin- 
cially, ' Firestone,' and by English geologists the ' Upper 
green-sand.' It sometimes consists of loose siliceous 
sand, containing grains of silicate of iron, but often of 
firm beds of sandstone and chert. 
2. Blue clay or calcareous marl, called provincially Gault. 
3. Lower green-sand, a very complex group consisting of 
grey, yellowish, and greenish sands, ferruginous sand 
and sandstone, clay, chert, and siliceous limestone. 
4. Weald clay, composed for the most part of clay without 
intermixture of calcareous matter, but sometimes in- 
cluding thin beds of sand and shelly limestone. 
5. Hastings sands, composed chiefly of sand, sandstone, clay, 
and calcareous grit, passing into limestone ** 
The first three formations above enumerated are of marine 
origin, the last two, Nos. 4 and 5, contain almost exclusively 
the remains of fresh-water and amphibious animals. But it is 
not our intention at present to enlarge upon the organic remains 
of these formations, as we have merely adverted to the rocks in 
order that we may describe the changes of position which they 
have undergone, and the denudation to which they have been 
exposed since the commencement of the Eocene period, — mu- 
tations which, if our theory be well founded, belong strictly to 
the history of tertiary phenomena. 
By a glance at the map, the reader may trace at once the 
* For an account of these strata in the south-east of England, see Mantell's 
Geology of Sussex, and Dr. Fitton's Geology of Hastings, where the memoirs of 
all the writers on this part of England are referred to. 
