Old Red volcanic rocks and brings down an important development
of Carboniferous strata occupying the southern part of the county.
These belong mainly to the Coal-measures and comprise a number of
valuable coal-seams which have been extensively worked. The
Clackmannan field is the northern continuation of the great
Lanarkshire basin which extends northwards by Slamannan, Falkirk and
the Carron Ironworks to Alloa. Along the eastern margin between
Cairnmuir and Brucefield the underlying Millstone Grit, consisting
mainly of false-bedded sandstones, comes to the surface. Close to the
river Devon south of Dollar the Vicars Bridge Limestone, which there
marks the top of the Carboniferous Limestone series, rises from
beneath the Millstone Grit. The structure of the Clackmannan field is
interesting. The strata are arranged in synclinal form, the highest
seams being found near the Devon ironworks, and they are traversed by
a series of parallel east and west faults each with a downthrow to the
south, whereby the coals are repeated and the field extended. During
mining operations evidence has been obtained of the existence of a
buried river-channel, filled with boulder clay and stratified deposits
along the course of the Devon, which extends below the present
sea-level and points to greater elevation of the land in pre-glacial
time. An excellent example of a dolerite dyke trending slightly north
of west occurs in the north part of the county where it traverses the
volcanic rocks of Lower Old Red Sandstone age.

_Industries._--The soil is generally productive and well cultivated,
though the greater part of the elevated range which is interposed
between the carse lands on the Forth and the vale of Devon at the base
of the Ochils on the north consists of inferior soils, often lying upon
an impervious clay. Oats are the chief crop, but wheat and barley are
profitably grown. Sheep-farming is successfully pursued, the Ochils
affording excellent pasturage, and cattle, pigs and horses are also
raised. There is a small tract of moorland in the east, called the
Forest, bounded on its northern margin by the Black Devon. Iron-ore
(haematite), copper, silver, lead, cobalt and arsenic have all been
discovered in small quantity in the Ochils, between Alva and Dollar.
Ironstone--found either in beds, or in oblate balls embedded in slaty
clay, and yielded from 25 to 30% of iron--is mined for the Devon
ir