Excerpt from The Journal of Physical Chemistry, 1909, Vol. 13 There is, I think, little doubt that some such action does take place; during the exposure there is a constant transference of atoms, till after a certain stage there is an ex cess of silver in the most exposed parts, and the mercury is deposited more readily upon the less exposed parts, or more or less equally all over the plate. Draper also found the Daguerreotype plates were acted on by the red and blue rays of the spectrum, in oppo site ways, similarly to the action noticed by Ritter with sil ver chloride. 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.