[This illustration is a photo-wood-engraving from a model by Mr. Nasmyth. It has been kindly lent for this work by Messrs. Bradbury, Evaus, & Co.] HANDBOOK OF ASTRONOMY. BY DIONYSIUS LARDNER, D.C.L. FORMERLY PROFESSOR OF NATURAL PHILOSOPHY AND ASTRONOMY IN Third Edition, Rebised and Edited by EDWIN DUNKIN, F.R.A.Ş. Superintendent of the Altazimuth Department, Royal Observatory, Greenwich. WITH ILLUSTRATIONS ON STONE AND WOOD. LONDON: JAMES WALTON, BOOKSELLER AND PUBLISHER TO UNIVERSITY COLLEGE, 137 GOWER STREET. 1867. PREFACE. Ir has been the purpose of the Author in the composition of this work to lay before the reader, in a clear and concise manner, the principles of astronomy, developed and demonstrated in ordinary and popular language, capable of being understood by those who may be possessed of an average amount of general knowledge. Perhaps at no time more than the present, when by the influence of the Oxford and Cambridge middle-class examinations, the education of the youth of the present generation is receiving unusual attention, has the want been more felt of elementary works on the different branches of scientific knowledge, possessing sound and reliable information expressed in language attractive to the reader. The study of such works would prepare him for more advanced treatises on the separate sciences. In the present edition of this work the Editor has endeavoured so to arrange the various sections of the science, as to exhibit to the inquiring reader the various movements and physical peculiarities of the different members of the solar system, without embarrassing his mind with mathematical symbols; for though symbolical explanations may seem to the advanced student to be a necessary adjunct for the proper elucidation of the different problems, yet it not unfrequently happens that the reader, with less mathematical proficiency, would altogether fail in the study of this science, were it not for the assistance afforded by popular and elementary works written in a lan 3317 guage comprehended by all. To the student of the higher or mathematical branches of astronomy, this work, however, will also be found interesting and instructive, as he will find information of the most valuable kind in it, for much of which he may look in vain in works of higher pretensions. It is well known that students may pass through their educational course without acquiring even a general knowledge of geometry and algebra. To all such persons, mathematical treatises on astronomy must be sealed books. Such students, notwithstanding their inability to understand works of that kind, may acquire a considerable acquaintance with this science, by consulting the various divisions of a work like the present, which though free from the usual symbols of mathematical explanations, is founded on reasoning sufficiently satisfactory and conclusive. The rapid succession of discoveries by which astronomical knowledge has been extended during the last twenty-two years has rendered elementary works on astronomy, published previously to 1845, to a certain extent, obsolete; while the increasing taste for the cultivation of the science, and the multiplication of private observatories and amateur observers, have created a demand for treatises, which shall comprise not only explanations of the movements of the earth and the other bodies of the solar system, but also illustrations of the physical appearances of the different planets, the information on which can only otherwise be obtained by reference to the Transactions of the various scientific societies of different countries, formed for the encouragement of astronomy and the other physical sciences. In illustration of this, we have only to refer the reader to the results which have been obtained from the researches of original inquirers, and from the labours of observers, which have been carefully reviewed, and from which large selections have been made, and presented to the reader in a popular and instructive form. In cases where the subject required graphic |