Excerpt from The Practical Astronomer: Comprising Illustrations of Light and Colours; Practical Descriptions of All Kinds of Telescopes; The Use of the Equatorial-Transit; Circular, and Other Astronomical Instruments As Light is the foundation of astronomical science, and of all the instruments used for celestial observation, a brief description is given of the general properties of light - of the laws by which it is refracted and reflected when passing through different mediums - and of the effects it produces in the system of nature - in order to prepare the way for a clear understanding of the princi ples on which optical instruments are constructed, and the effects they produce. 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.