Excerpt from A Dictionary of Applied Physics, Vol. 1 of 5: Mechanics, Engineering, Heat The efficiency. - Several kinds of efficiencies are recognised as applicable to pumps and blowers; of these the mechanical efficiency, or the ratio of the useful work done to the total work expended, is alone applicable to all types. Both terms of the ratio need further definition to rid them of ambiguity. The work expended is usually taken to mean either (a) the work expended on the gas in giving to it energy, com pressive, kinetic, or thermal, or (b) the work supplied to the mechanism of which the pump consists, including that lost in friction of solid or liquid parts. The efficiency reckoned with (a) is often termed the gas efficiency; that reckoned with (b) the over-all efficiency. 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.