Physical Structure and older stratified Deposits of Devonshire. 637 



tified,as well as unstratified rocks^, with which they come in contact. The great 

 series of rocks, therefore, which occupy this third region, are the newest depo- 

 sits of our north and south section : and without prejudging their place in the 

 British system, we may describe them conveniently as the culmiferous series, 

 inasmuch as all the culm works of the county have been opened in them. 



The extent and true geological position of this great deposit had been ge- 

 nerally misunderstood ; for though certain beds of culm had been long known 

 and extensively worked in North Devon, yet they had always been described 

 as mere bands subordinate to the old greywacke system ; and had never been 

 regarded either as occupying a great overlying trough, or as composing a 

 distinct formation. Hence, also, the black limestones which appear on both 

 sides of the great trough and form a part of the base of the culm- series, had 

 been confounded with the other calcareous bands of the inferior groups. 



4th. The fourth region into which we divide the county of Devon is occu- 

 pied by the granitic rocks extending through the whole of Dartmoor. 



5th. The fifth and last region includes all the remaining portion of the 

 county ; bounded towards the north, partly by the granite of Dartmoor, and 

 partly by the southern skirt of the culm measures ; and towards the south, by 

 the long line of cliffs extending from Babacombe Bay to the west side of 

 Plymouth Sound. 



We think that the five regions, above enumerated, form natural subdivisions, 

 — not laid down artificially, to facilitate description, but well characterized, 

 both by their geographical features and their physical structure. 



Passing over the first region, we shall proceed to describe the second or 

 hilly region of the north coast ; showing, by help of natural sections, into what 

 groups it may be conveniently subdivided. We purpose afterwards, in like 

 manner, briefly to describe the fifth or southern region, to establish its sub- 

 divisions, and to bring them, as far as we are able, into comparison with the 

 subdivisions of the second region. We shall then be prepared to describe 

 the culmiferous rocks of the third region, and to show the relation they bear 

 to all the rocks against which they abut, or on which they rest. In this way, 

 after briefly noticing the general position of the Dartmoor granite, among the 

 surrounding strata, and the characteristic phenomena at its junction with 

 them, we hope to determine the whole sequence of the formations between 

 the north and south coast of the county. 



Our task does not, however, terminate here ; for by help of all the analogies 

 with which we are acquainted, and more especially by help of the structure 

 and organic remains of the several formations, we shall, in future communica- 

 tions, endeavour to bring them into comparison with the older groups of other 



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