Excerpt from A Compendium on Railway Car Bearings The resistance called friction, and the best means of reducing it in machinery, constitute one of the most im portant - though by no means, the best understood -subjects of practical mechanics. What we know concerning it is due entirely to experiment, and some of the results are what might not have been expected prior to experiment. As it is impossible to render two surfaces perfectly smooth and hard if they are pressed together, the slight and insensible eleva tions of the one will interlock with the corresponding depressions of the other, and to produce motion between them, these slight asperities, must be abraded, or the surfaces themselves must be partly or wholly separated, resulting, in either case, in a loss of power. While on the one hand, friction 'is a constant and important element as a source of waste in motive power, it is, on the other hand, an indis pensable condition, not only to mechanical motion, but to the stability of all structures, and to human existence itself. Its reduction to the lowest possible point in one case, and its retention to the highest possible degree in another, con stitare one of the most perplexing problems in mechanics. 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.