Since then two other editions of this translation have appeared, in which the alterations contained in the successive German editions have been embodied in the form of appendices. In the seventh German edition, however, which appeared at Leipsic (F. A, Brockbaus) in 1912, there have been more profound modifications in the plan of Professor Mach's work, which are shortly referred to in the preface to that edition. Many things are added and some things are omitted. Among the parts omitted are the prefaces to all of the German editions except the first, and a new preface to the seventh edition has been added. The most extensive additions relate to recent historical researches on the work of Galileo's precursors and the early work of Galileo himself; and the book is dedicated to the late Emil Wohlwill, of whose researches much use has been made. 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.