Excerpt from Spectroradiometric Investigation of the Transmission of Various Substances When it is possible to sacrifice spectral purity in order to obtain high intensity, some of these substances, which have bands of transmission which are 70 to 80 per cent at the maximum, may be more efficient than a spectrometer in producing stimuli of Spectral radiation of high intensity and covering a large area. The apparatus used for determining the transmissions in the visible (yellow to red) and infra-red parts of the spectrum con sisted of a mirror spectrometer, a fluorite prism, and a vacuum bismuth-silver thermopile, described in previous papers. 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.