rs
of Dartmoor have a shorter and more rapid course.

_Geology._--The greatest area occupied by any one group of rocks in
Devonshire is that covered by the Culm, a series of slates, grits and
greywackes, with some impure limestones and occasional radiolarian
cherts as at Codden Hill; beds of "culm," an impure variety of coal,
are found at Bideford and elsewhere. This series of rocks occurs at
Bampton, Exeter and Chudleigh and extends thence to the western
boundary. North and south of the Culm an older series of slates, grits
and limestones appears; it was considered so characteristic of the
county that it was called the DEVONIAN SYSTEM (q.v.), the marine
equivalent of the Old Red Sandstone of Hereford and Scotland. It lies
in the form of a trough with its axis running east and west. In the
central hollow the Culm reposes, while the northern and southern rims
rise to the surface respectively north of the latitude of Barnstaple
and South Molton and south of the latitude of Tavistock. These
Devonian rocks have been subdivided into upper, middle and lower
divisions, but the stratigraphy is difficult to follow as the beds
have suffered much crumpling; fine examples of contorted strata may be
seen almost anywhere on the north coast, and in the south, at Bolt
Head and Start Point they have undergone severe metamorphism.
Limestones are only poorly developed in the north, but in the south
important masses occur, in the middle and at the base of the upper
subdivisions, about Plymouth, Torquay, Brixham and between Newton
Abbot and Totnes. Fossil corals abound in these limestones, which are
largely quarried and when polished are known as Devonshire marbles.

On the eastern side of the county is found an entirely different set
of rocks which cover the older series and dip away from them gently
towards the east. The lower and most westerly situated members of the
younger rocks is a series of breccias, conglomerates, sandstones and
marls which are probably of lower Bunter age, but by some geologists
have been classed as Permian. These red rocks are beautifully exposed
on the coast by Dawlish and Teignmouth, and they extend inland,
producing a red soil, past Exeter and Tiverton. A long narrow strip of
the same formation reaches out westward on the top of the Culm as far
as Jacobstow. Farther east, the Bunter pebble beds are represented by
the well-known pebble depos