Page:The parochial history of Cornwall.djvu/36

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ceeding along the ridge towards the Land's End, the next, or St. Austel patch of granite will be found, much less than the last, hut more interesting both in a scientific and a commercial point of view. In addition to the kinds of granite already noticed, it contains beds of talcose granite, or protogine, which by its decomposition furnishes that valuable substance china clay or kaolin, many thousand tons of which are annually exported for the potteries. The third, or Redruth patch of granite, affords many varieties of this rock, and has been well explored by numerous mines which have been productive in both tin and copper ores, affording also to the mineralogist a great variety of rare specimens. But the fourth, or Land's End granite, is by far the most important to the geologist, for the land becoming here very narrow, the sea has produced cliff-sections, both in the granite, and also at its point of junction with the slate, exhibiting many interesting phenomena. Among these, the veins of granite in the slate are beautifully displayed, and have long been a great attraction to geologists; but the modes in which these rocks meet and unite, are not less deserving of notice. But for a detailed description of these curious facts, the reader may be referred to my "Treatise on Primary Geology."

Besides these four principal patches of granite, there are four others: 1st. that of Kitt Hill, near Callington; 2nd. that of Tregonning and Godolphin, near Helston; 3d. that of Cligga Point, near St. Agnes; and lastly, that of the celebrated St. Michael's Mount. The two first are of some size,