Excerpt from Maryland Geological Survey, 1919 The Survey is also indebted to Dr. E. O. Ulrich of the U. S. Geological Survey for permission to incorporate in this volume a set of his paleo geographic maps covering the Cambrian and Ordovician formations. 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.