10 
SOILS AND SPECIES. 
BOTANICAL DIVISIONS. 
HE botanical divisions are based upon the surface geology 
of the County so far as practicable, and are arranged in 
order of formations, beginning with the oldest and designated by 
letters indicative of the main formation. Wherever, besides the 
proper formation of a division, parts of other formations are 
included in it, this will be pointed out under that division. It 
seems unnecessary to describe the boundaries of the divisions, as 
they will be sufficiently indicated in the map. 
L.—MOUNTAIN LIMESTONE.—This, the oldest geologi- 
cally, occupies the west central part of the County. It is 
interpolated here and there with sheets of contemporaneous 
lava (toadstone), though in some cases the toadstone is a later 
intrusion, as near Peak Forest and Tideswell. It has three 
small outliers—at Ashover and Crich eastwards, and at Snelston 
Common southwards, besides another south of the Trent at 
Ticknall and Calke. By the action of water, deep ravines or 
canons have been carved out on its west, north and east borders, 
the well-known dales, where the characteristic flora mostly 
abounds. The main plateau rises here and there into rounded 
hills, the dales present tiers of wall-like cliffs along their sides. 
Two small beds of glacial deposit overlie part of the area on the 
east side of Mappleton, and from Ashbourne to Ashbourne 
Green. The mountain limestone is succeeded on all sides by the 
Yoredale Rocks, well seen at Mam Tor above Castleton, some of 
them on the south border being included in this division. 
