Excerpt from A Catalogue of Physical Instruments: Catalogue 17 Under each subject we have aimed to include only those pieces best suited for the particular experiment and demonstration. In making this selection from our complete line we have found that it requires even greater judgment to determine what to omit than it does to determine what to include, but unnecessary duplication has been carefully avoided. We realize that the instructor whose duty it is to equip or improve a laboratory should buy only the best and at the same time strive to make his appropriation go as far as possible. A large proportion of the articles offered have been designed and developed in our own laboratory under the supervision of men whose training and experience have well fitted them for the task. In addition we have made a careful selection from the best scientific establishments of the world. In making the selection we have been guided by numerous suggestions received from our customers, an obligation which we are pleased to acknowledge at this time, with the hope that all of our customers will feel it an obligation as well as a pleasure to favor us with any further suggestions which their experience develops. 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.