Download or read book Henley's Encyclopaedia of Practical Engineering and Allied Trades, Vol. 7 written by Joseph Gregory Horner and published by Forgotten Books. This book was released on 2017-11-06 with total page 554 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excerpt from Henley's Encyclopædia of Practical Engineering and Allied Trades, Vol. 7: A Practical and Indispensable Work of Reference for the Mechanical Engineer, Designer, Draftsman, Shop Superintendent, Foreman and Machinist Ores occur in all classes of rock in the earth's crust; in igneous rocks which were once in a molten state, in sedimentary rocks formed by the deposition Of material by water, and in metamorphic rocks, which, originally laid down by the action of water have been changed by the action of fire, pressure, or chemical agency. Some ores, as well as native metals are found as alluvial deposits which have been brought down from higher grounds through the agency of water and deposited in the river valleys. In the case Of gold such deposits are called placers. 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.