Excerpt from Electric Switches: For Use in Gaseous Mines The investigation described in this bulletin was preliminary in nature and was undertaken principally to obtain information upon which to base future tests of a similar character. It was not the intention of the Bureau of Mines to approve any of the switches tested. The demand in this country for switches especially de signed for mine service has not in the past been sufficiently great to interest manufacturers in the development of such switches. Con sequently it is not surprising that only one of the switches submit ted to the bureau for test appeared to be a practical design for general mine use. 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.