Excerpt from The Galvanometer: A Series of Lectures For purposes of absolute measurement the coils of the galvanometer must be of known dimensions, they must be at a known distance from the needle, and the latter must be situated in a magnetic field of known intensity. The simplest form, which is also that most frequently met with in practice, consists of one or more circular coils mounted vertically in the magnetic meri dian. Where a single coil is used the needle is in its axis. When there is more than one coil, these have a common axis in which the needle hangs. 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.