Excerpt from Recent Developments in Drawing by the Aid of Projection Apparatus, Used on the House Lighting System
In the first place one must possess an arc lamp in which the carbons are held at right angles to each other; and, in passing, it is gratifying to remember that the now so widely used right angled arc lamp for projection, was devised in I894 by Mr. Albert T. Thompson of Boston. Without a lamp for holding the carbons in this position so that the one giving the light can remain constantly in the optic axis, the small drawing outfits would be practically impossible.
The carbons must be small, from the small current used, viz.: 3 to 6 amperes; and they should be soft cored. A small arc lamp is a convenience, but any arc lamp designed for the carbons at right angles can be used by employing bushings or adapters to hold the small carbons.
Either direct or alternating electric current can be used. One must know which current is on his house lighting system, and also the voltage. Both these facts can be learned by inquiry at the office of the electric lighting company furnishing the electricity.
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.show more