Excerpt from On the Determination of the Mean Horizontal Intensity of Incandescent Lamps The lamp was first rotated at about 420 r. P. M. And readings were taken. Then measurements were made every 100 in the horizontal plane with the lamp stationary, and finally the lamp was rotated again at 420 r. P. M. If we call the first rotating value then the value of mean horizontal intensity obtained by the point-to point method is and the value found on subsequent rotation In other words, the results obtained by the two methods, the speed of rotation being 420 r. P. M., agree to within or per cent, which is within the range of experimental error. Since in this type of lamp the filament is well supported, one would not expect as large errors as for some other types, such as the double filament lamp (fig. 1, No. In this type of lamp, which was next studied, the filament consists of two long, slender loops, entirely unsupported except at the leading-in wires. Denoting by the value of mean horizontal candlepower obtained at the beginning at a speed of 3 50 r. P. M., the value found by the point-to-point method every 100 is 5, and the value obtained at the end at a speed of 3 50 r. P. M. Is This decrease of 0. 5 per cent at a speed of 3 50 r. P. M. Is in very good agreement with that obtained in the previous investigation using the rotating mirror method. The mean of a number of determinations using this method indicated a decrease of per cent at a speed of 500 or 600 r. P. 111. 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.