Book excerpt: Excerpt from Influence of Quality of Gas and Other Factors Upon the Efficiency of Gas-Mantle Lamps Btu, and of coal gas of 56 5 Btu, these were selected as the typical gases to be studied. For the sake of comparison and further study of certain variables, some specially enriched gases of higher heating value were also used in a few cases. Since typical commercial gases vary from time to time within certain limits, both as to com position and heating value, it was not considered necessary to maintain exactly the same quality of gases throughout the various series of tests; nor was it practicable to do so. An effort was made, however, to prevent as far as possible variations between sets of observations which were intended to be comparable. 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.