Excerpt from Index to the Popular Science Monthly: From 1872 to 1892, Including Volumes I to XL and the Twenty-One Numbers of the SupplementBut all this has now been changed. The last half of the nineteenth century will long be memorable as the period during which science achieved a prominent if not a leading place in nearly every department of human activity. The wonderful advance of discovery, closely followed by numerous practical applications, has wrought a revolution in many fields, until in the arts, in commerce, in education, and even in the pro fessions, science may justly claim to exercise a controlling in¿uence.With all this there has come an enormous increase in the volume of scientific literature. Scores of scientific periodicals are engaged in the work of disseminating the results of investigation and books by the hundred are published every year in which the methods and conclusions of science are given more permanent record. The accumulation of ma terial from this ceaseless and ever-increasing activity is already so great that ready means of access to it becomes an urgent need of the hour.But it is only with a subdivision of this great body of knowledge that we are here specially concerned. In the early days of the scientific awakening just alluded to, it was only natural that the results obtained by workers in science should for the most part remain the possession of the student and investigator. That science, however, had a message for the people was not long in being perceived. Under the stimulus sup plied by a few enthusiastic public teachers there gradually arose a demand for this new kind of knowledge that would brook no refusal. In obedi ence to this desire of the public we have seen issuing from the press during the last twenty-five or thirty years a steadily growing stream of popular scientific literature embodying the ablest thought of the time, and much of it the product of our most distinguished scientific men.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis 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.