116 The Flora of Wiltshire. 
sions, the Cretaceous and the Oolitic. The difference between these 
is strongly marked, and the beautiful undulations of our chalk 
downs with their simple clothing of fine turf, contrast very remark- 
ably with the rich wooded valleys and pastures of the middle oolites. 
The chalk may be considered, from its extent, as the most striking 
geological feature, occupying fully one half of the whole area of 
the county, forming as it does the extensive downs, which over- 
spread the eastern, central, and southern parts; and there can be 
but little doubt that a stratum so extensive and differing so much as 
it does, both chemically and mechanically from most of the oolitic beds, 
will be found to possess certain peculiarities of Floral distribution. 
This we expect will prove to be the case as our knowledge of the 
botany of the county becomes more extended. 
The Cretaceous system, includes, besides the Chalk, the Upper 
Green sand, Gault, and Lower Green sand, and in this county these 
usually follow with considerable regularity. The outliers of the 
chalk escarpment form terraces or gentle slopes along the bases of 
the hills. 
The Lower Green sand has not hitherto been observed in the 
southern division. _ 
The Cretaceous strata of Wilts are comprised in the following 
Table. 
STRATA. EXAMPLES. 
Upper chalk or chalk with flints, Near Salisbury, Marlborough, and 
on most of the higher chalk hills. 
Lower chalk and chalk marl, Towards the bases of most of the 
chalk hills, as at Bishop’s Can- 
nings, Cliff Wancy, Warmin- 
f ster, &c. 
Upper Green sand, Devizes, Warminster, Pewsey. 
Gault, Devizes, Crockerton, Rowde. 
Lower Green sand, Seend, Spye Park, Calne. 
Wiltshire furnishes examples of most of the members of the 
Upper and Middle oolites, and the following Table exhibits a list 
