[Illustration: THE AUTHOR’S OBSERVATORY.] 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, A PARTICULAR ACCOUNT OF THE EARL OF ROSSE’S LARGE TELESCOPES, AND OTHER TOPICS CONNECTED WITH ASTRONOMY. BY THOMAS DICK, LL.D. AUTHOR OF THE “CHRISTIAN PHILOSOPHER,” “CELESTIAL SCENERY,” “THE SIDEREAL HEAVENS,” &C. &C. Illustrated with One hundred Engravings. SEELEY, BURNSIDE, AND SEELEY, FLEET-STREET, LONDON. MDCCCXLV. PRINTED BY L. SEELEY. PREFACE. The following work was announced several years ago in the preface to the volume on “The Sidereal Heavens;” since which time numerous enquiries have been made after it by correspondents in England, the West Indies, and America. It was nearly ready for publication three years ago; but circumstances over which the Author had no controul, prevented its appearance at that period. This delay, however, has enabled him to introduce descriptions of certain instruments and inventions which were partly unknown at the time to which he refers. The title “Practical Astronomer” has been fixed upon, as the shortest that could be selected, although the volume does not comprise a variety of topics and discussions generally comprehended in this department of astronomy. The work is intended for the information of general readers, especially for those who have acquired a relish for astronomical pursuits, and who wish to become acquainted with the instruments by which celestial observations are made, and to apply their mechanical skill to the construction of some of those which they may wish to possess. With this view the Author has entered into a variety of minute details, in reference to the construction and practical application of all kinds of telescopes, &c. which are not to be found in general treatises on Optics and Astronomy. 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 principles on which optical instruments are constructed, and the effects they produce. As this, as well as every other physical subject, forms a part of the arrangements of the Creator throughout the material system--the Author has occasionally taken an opportunity of directing the attention of the reader to the Wisdom and Beneficence of the Great First Cause, and of introducing those moral reflections which naturally flow from the subject.