Excerpt from The Luminous Properties of Electrically Conducting Helium Gas In filling standard tubes with helium the greatest difficulty is in freeing the electrodes from hydrogen. This is best accomplished by steady pumping while a heavy current is passing through the tube. After but a few minutes pumping nearly all of the im purities except hydrogen will disappear, indicating, perhaps, that the interior walls are clear of gas. After about fifteen minutes fur ther pumping the hydrogen pressure drops abruptly. This, I take it, is when the disk portions of the electrodes are depleted of included hydrogen. To completely clear the stems of the electrodes requires further pumping and current for perhaps an hour. N 0 air or helium should be admitted during this process, as it makes the complete elimination of the hydrogen much more tedious and difficult. 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.