Excerpt from The Technograph, Vol. 28: A Quarterly Publication of the Engineering Societies of the University of Illinois; November, 1913 The real problem in planning for artificial illumination is there fore not so much the amount of light as the manner in which it is applied. The ideal light-source would naturally be one which would give a uniform number of rays upon the work from all directions. A condition which may be approached with daylight. But daylight is free, artificial light costs, and economy must be considered. As a result we find tables stating definitely the light in foot-candles desirable for different classes of interiors such as parlors, offices. Drafting-rooms, etc., these tables indicating the probable minimum lighting which most eves would need to dis cern clearly the objects in the room or to perform the work re quired of them. In many cases the values given could be lowered if good distribution and diffusion were assured, as is'later ex plained. Distribution and diffusion are by no means synonymous terms. By good distribution is meant uniform lighting, usually having reference to the working plane, a plane parallel to the floor and from two to three feet above it. Such a result may be se cured from a point - source equipped with the proper reflector. (see Fig. To be diffused, the light rays producing illumina tion at any point must come from all directions so that there can be no regular reflection. It is sometimes impossible to secure this effect because of the nature of the material, as in the case of polished metal or furniture, but no installation should be counte nanced where conditions of good distribution and diffusion are not at least approached. 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.