Page:Cornwall (Salmon).djvu/23

 GENERAL PHYSICAL FEATURES Granite is very largely quarried in Cornwall, and W. of St. Austell Diorite is dug for road metal. The Scilly Islands consist of about 145 islets or rocks, of which St. Mary, the largest, is about 3 miles long and 2^ miles broad. The highest point of the island is 204 feet above sea- level. The Scilly Islands are composed almost entirely of a coarse kind of granite which is not largely quarried. The metalliferous wealth of the duchy lies in its granite and slate. The land supplies little fuel — no coal, and not much peat ; and this has proved one of the chief handicaps to mining enterprise. There are four distinct outcrops of granite. The first of these, on the Bodmin Moors, gives Cornwall its highest hill. Brown Willy. The next patch is around Hens- barrow, a few miles from St. Austell; the next is at Carnmenelez, near Redruth; and the last is at Land's End. Beyond this, the Scilly Islands themselves are simply the peaks of sub- merged granite mountains. Bodmin Moors, lying between Launceston and Bodmin, are very much like a replica of Dart- moor, similarly strewn with granite tors, traces of prehistoric habitations, and gaping bogs. If anything, the bogs of Bodmin Moors are the worse. Northward, near the coast, we find the greatest proftision of Devonian slate; southward are the ichthyolitic " Polperro fossils," amid limestones and sandstones. At the Lizard is the most interesting geologic formation of all, s