Excerpt from Mineral Resource Research, 1946-1947, by the Illinois State Geological Survey Special high-powered microscopes reveal details of the structure of clays and enable Survey scientists to predict their behavior and to discover new uses for them. Illinois quarries produce large tonnages of limestone for agricultural use, road building, rail road ballast, and many other uses. 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.