Page:The parochial history of Cornwall.djvu/33

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AN INTRODUCTION

TO

THE GEOLOGY OF CORNWALL.

BY Dr. BOASE.

THE geological notices inserted in this Work, are necessarily so brief and so unconnected, on account of the alphabetical arrangement of the parishes, that it is desirable that a few introductory remarks should be made that this defect may be in some measure obviated.

Cornwall does not possess a great variety of rock formations, being composed of primary and transition or intermediate groups, covered here and there with deposits of gravel, sand, and clay, which belong to the modern epoch. But this limited range of formations is more than compensated for by the great facilities which the geologist here enjoys in his investigations; the very extended line of cliffs which deeply indent the Cornish shores proffer numerous and instructive sections; and the vast mining operations have brought to light most important phenomena. Indeed, no country of equal extent can, in these combined advantages, be compared with Cornwall.

On a general view of this country, the surface exhibits two systems of valleys; one running paral-

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