ii
THE AUTHOR’S OBSERVATORY.
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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.
iv
v
PRINTED BY L. SEELEY.
PREFACE.
The following work was announced several years ago inthe preface to the volume on “The Sidereal Heavens;”since which time numerous enquiries have been madeafter it by correspondents in England, the West Indies,and America. It was nearly ready for publication threeyears ago; but circumstances over which the Authorhad no controul, prevented its appearance at that period.This delay, however, has enabled him to introduce descriptionsof certain instruments and inventions whichwere partly unknown at the time to which he refers.
The title “Practical Astronomer” has been fixedupon, as the shortest that could be selected, althoughthe volume does not comprise a variety of topics anddiscussions generally comprehended in this departmentof astronomy. The work is intended for the informationof general readers, especially for those who haveacquired a relish for astronomical pursuits, and whowish to become acquainted with the instruments bywhich celestial observations are made, and to apply theirmechanical skill to the construction of some of those whichthey may wish to possess. With this view the Authorhas entered into a variety of minute details, in referenceto the construction and practical application of all kindsviof telescopes, &c. which are not to be found in generaltreatises 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 oflight—of the laws by which it is refracted and reflectedwhen passing through different mediums—and of theeffects it produces in the system of nature—in order toprepare the way for a clear understanding of the principleson which optical instruments are constructed, andthe effects they produce.
As this, as well as every other physical subject, formsa part of the arrangements of the Creator throughoutthe material system—the Author has occasionally takenan opportunity of directing the attention of the readerto the Wisdom and Beneficence of the Great FirstCause, and of introducing those moral reflections whichnaturally flow from the subject.
The present is the ninth volume which the Author haspresented to the public, and he indulges the hope thatit will