Page:The parochial history of Cornwall.djvu/34

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GEOLOGICAL INTRODUCTION

lel with the central ridge, which is highest near Launceston, and gradually, but irregularly, declines till it terminates at the Land's End, in cliffs about a hundred feet in height; the other intersecting the longitudinal valleys at right angles; and as all the intermediate hills are more or less rounded, the country has an undulating appearance in both directions, not unaptly compared to the waves of the sea. Through these two systems of valleys, the rivers flow, seeking outlets into the sea by the nearest continuous descent; sometimes they effect this along the longitudinal, at others through the transverse valleys, receiving tributary streams on either hand from the lateral valleys, or curved hollows which they intersect. But sometimes the river is diverted in its course more than once, in consequence of the concavity of a cross curve rising above its level or by that of the other system descending below this point by which irregularity the stream is compelled to flow along the more favourable drainage; thus the Camel rises about four miles from the sea, in the moors near Davidstow, and flows more than twenty-five before it empties itself into the sea at Padstow. In the hollows of these valleys the drainage is often sufficiently obstructed to produce marshy ground; but seldom of such extent as to deserve the name of a lake.

As regards the soil, on the high grounds it is frequently very shallow and barren; but in the valleys it is very productive, and here and there is well wooded, more particularly on the southern coast. On the northern coast, in the vicinity of the sea,