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THE

ELEMENTS

OF

ASTRONOMY:

FOR

COLLEGES, SCHOOLS, AND PRIVATE STUDENTS.

WRITTEN FOR THE MATHEMATICAL COURSE OF

JOSEPH RAY, M.D.,

BY

SELIM H. PEABODY, M. A.,

TEACHER OF NATURAL SCIENCES IN TH" CH CAGN BIGH SCHOUL

CINCINNATI:
WILSON, HINKLE & CO.

PHIL’A: CLAXTON, REMSEN & HAFFELFINGER.

NEW YORK: CLARK & MAYNARD.

THENTA YORK
1:- LIC LIBRARY

478725

ASTOR, LENOX AND
TEA FICATIONS.

Entered according to Act of Congress, in the year 1869, by

WILSON, HINKLE & CO., In the Clerk's Office of the District Court of the United States,

for the Southern District of Ohio.

ELECTROTYPED AT THE
FRANKLIN TYPE FOUNDBY.

CINCINNATI

PREFACE.

Branch NOV 26 1909

Muhlenbey

In this work I have endeavored to describe and explain the Mechanism of the Solar System and of the Stellar Universe. Though written for pupils in the higher grades of public schools, it may be found useful in institutions of still higher rank, and as a foundation for more extended research by the private student.

Although well aware that the rigid principles of mathematics and mechanics form the sole foundation of high astronomical attainment, I have carefully avoided abstruse mathematical demonstrations. Most who study Astronomy desire an accurate knowledge of facts and principles, but need neither for mental culture nor for practical use such a mastery of methods as should fit them to become even amateur astronomers. For such I have aimed to furnish needed information and instruction. I have assumed that my readers know only the simplest principles of geometry and algebra, and the plainest facts of mechanics and physics. The rest I have endeavored to supply as needed.

The liberality of Publishers has enabled me to insert an unusual number of illustrations. Of the telescopic views, selected from the best authorities, some have lately found their way into American text-books; others appear now for the first time. The beautiful experiments of Foucault on the Rotation of the Earth, of Fizeau on Light, and of Plateau on Rotation,

(iii)

Transfer from Circ. Dept.

have not been described hitherto in works of this grade. The same is true of the elegant apparatus of Bache for measuring base lines, reference having usually been made to the clumsier machinery of the English or French. Many of the diagrams are new, the fruits of hard work in the class-room.

If the omission of the figures of men, animals, and serpents from the star-maps seems to any a questionable innovation, I have to say that my own experience as a teacher long since convinced me that those monstrosities hinder rather than help; and that my practice is sanctioned by Arago, Herschel, Lockyer, Proctor, Guillemin, and others, foremost astronomical writers of the present day,

The Circumpolar Map is drawn on the equidistant projection, the increase in polar distance being always equal to the increase in circular arc. The Equatorial Maps have for base lines the meridian and the equinoctial — circles easily found, and always in the same position relative to the observer. The projection is the Polyconic, adopted by the U. S. Coast Survey for terrestrial maps, and now first used, so far as I am informed, for astronomical maps. Each tenth declination-parallel is assumed to be the base of a cone, tangent to the sphere in that circle; the spherical surface between that and the next higher parallel is projected into the conical surface, which is then developed upon a plane. As the maps extend but 30° on either side of the meridian, it is believed that the distortion, caused when a spherical surface is represented on plane, is reduced to a minimum. The stars have been carefully platted from Proctor's Tables.

The Astronomical Tables have been compiled chiefly from Chambers. Following the example of Herschel in his “Outlines,” and the advice of eminent American astronomers, I have retained

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