ELEMENTS OF ASTRONOMY, FOR SCHOOLS AND ACADEMIES, WITH EXPLANATORY NOTES, AND QUESTIONS FOR EXAMINATION. BY JOHN BROCKLESBY, A.M., PROFESSOR OF MATHEMATICS AND NATURAL PHILOSOPHY IN TRINITY COLLEGE, Hartford, "VIEWS OF THE MICROSCOPIC WORLD." Fully Illustrated. "Lift up your eyes on high, and behold WHO has created these things, that bringeth out NEW YORK: PUBLISHED BY FARMER, BRACE, & CO. AND SUCCESSORS TO PRATT, WOODFORD, AND CO. NO. 4, CORTLANDT-STREET. 1855. ENTERED, according to Act of Congress, in the year 1855, in the Clerk's Office of the District Court of Connecticut. STEREOTYPED BY RICHARD H. HOBBS, HARTFORD, CONN. C. A. ALVORD, Printer, 29 Gold-street. PREFACE. THE science of Astronomy, conversant as it is with the sublimest natural phenomena, has ever engaged the attention of mankind, even when, from century to century, scarcely any new revelation of the skies rewarded the labors of the astronomer. But at the present time, when discovery crowds upon discovery, and the whole field of astronomical research has been wonderfully enlarged, it has suddenly become invested with the charms and freshness of a new science; and all classes of society listen with wonder and delight to the recital of the lofty truths and amazing facts which it unfolds. In attempting, therefore, with many honored names, to cause Astronomy to descend from the dignified seclusion of the observatory, that she may walk as a familiar guest amid the lesser temples of knowledge, no apology is required for the motive that prompts the task how much soever it may be needed on account of the execution. In the present treatise the author has not sought to adapt its subject to the youthful mind, by curtailing the science of its fair proportions, and omitting every thing that requires patient and earnest study; but he has aimed to preserve its great principles and facts in their integrity, and so to arrange, explain, and illustrate them, that they may stand out boldly defined, and be clear and intelligible to the honest and faithful student,— this is all that can be done for a pupil, if a science is to be taught in its completeness and not in parts. The hill of science will always be a hill. Impediments and obstructions may be removed and the ascent rendered easier, but the hill cannot be leveled, it must be surmounted. Several peculiarities are contained in this text-book, which it is thought will be of material service to the pupil in obtaining a knowledge of the science. The most important of these we shall now briefly notice. I. It is usual, in most text-books on this science, to explain many astronomical phenomena by the apparent, and not by the real motions of the celestial bodies. In this treatise the opposite course is taken, wherever practicable; the explanations being based upon the real motions of the heavenly bodies. By pursuing this method, the subsequent acquisitions of the scholar are built upon the truth itself, and not upon what appears to be true. II. The mode of ascertaining the distances and magnitudes of the heavenly bodies is so simplified that any student, who understands the rule of proportion, can readily comprehend it. III. Scientific terms and expressions are explained by foot notes on the pages in which they occur; and in these notes are likewise embodied such illustrations and information as tend to elucidate the text. In the preparation of this manual, the author has had recourse to numerous standard works upon Astronomy, and-has brought up the subject to the present time. For information respecting recent astronomical discoveries, he is especially indebted to the treatises of Sir John Herschel and Mr. J. Russel Hind. HARTFORD, Feb. 19th, 1855. |