Excerpt from On the Igneous and Pyroclastic Rocks of the Berwyn Hills (North Wales) This constitutes a large portion of the Central Upland of Wales, consisting principally of Ordovician sediments, anked on three sides by formations of Silurian age which once entirely covered it. It is not intended here to enter into the detailed history of the sedimentary rocks, which, nevertheless, is highly essential for the correct interpretation of numberless faults, as yet unmapped, and variations in horizontal equivalents. The task is the correlation of notes recorded during a series of years in a resume of the nature and classification of the bedded and complementary hypabyssal igneous rocks of the region. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works."