Excerpt from Investigations as to Pneumatic-Tube Service for the Mails: Letter From the Postmaster-General, Submitting the Report of an Investigation as to Pneumatic-Tube Service for the Mails Headway. - The closest interval between tube carriers originally expected to be six seconds is now thirteen to fifteen seconds, so that the total number of letters dispatched one way per hour is rated at instead of, as in the early days. 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.