The Project Gutenberg eBook ofThe Practical AstronomerThis ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this ebook or online atwww.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook.Title: The Practical AstronomerAuthor: Thomas DickRelease date: March 24, 2017 [eBook #54420]Most recently updated: October 23, 2024Language: EnglishCredits: Produced by Chris Curnow, Wayne Hammond and the OnlineDistributed Proofreading Team at http://www.pgdp.net (Thisfile was produced from images generously made availableby The Internet Archive)*** START OF THE PROJECT GUTENBERG EBOOK THE PRACTICAL ASTRONOMER ***
This ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this ebook or online atwww.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook.
Title: The Practical AstronomerAuthor: Thomas DickRelease date: March 24, 2017 [eBook #54420]Most recently updated: October 23, 2024Language: EnglishCredits: Produced by Chris Curnow, Wayne Hammond and the OnlineDistributed Proofreading Team at http://www.pgdp.net (Thisfile was produced from images generously made availableby The Internet Archive)
Title: The Practical Astronomer
Author: Thomas Dick
Author: Thomas Dick
Release date: March 24, 2017 [eBook #54420]Most recently updated: October 23, 2024
Language: English
Credits: Produced by Chris Curnow, Wayne Hammond and the OnlineDistributed Proofreading Team at http://www.pgdp.net (Thisfile was produced from images generously made availableby The Internet Archive)
*** START OF THE PROJECT GUTENBERG EBOOK THE PRACTICAL ASTRONOMER ***
THE AUTHOR’S OBSERVATORY.
THE AUTHOR’S OBSERVATORY.
PRINTED BY L. SEELEY.
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 kindsof telescopes, &c. which are not to be found in general treatises on Optics and Astronomy.
AsLightis 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.
The present is the ninth volume which the Author has presented to the public, and he indulges the hope that it will meet with the same favourable reception which his former publications have uniformly experienced. It was originally intended to conclude the volume with a few remarks on theutilityof astronomical studies, and theirmoralandreligioustendency, but this has been prevented, for the present, in consequence of the work having swelled to a greater size than was anticipated. Should he again appear before the public as an author, the subject of discussion and illustration will have a more direct bearing than the present on the great objects of religion and a future world.
Broughty Ferry, near Dundee, August, 1845.
THEPRACTICAL ASTRONOMER.
Light is that invisible etherial matter which renders objects perceptible by the visual organs. It appears to be distributed throughout the immensity of the universe, and is essentially requisite to the enjoyment of every rank of perceptive existence. It is by the agency of this mysterious substance, that we become acquainted with the beauties and sublimities of the universe, and the wonderful operations of the Almighty Creator. Without its universal influence, an impenetrable veil would be thrown over the distant scenes of creation; the sun, the moon, the planets, and the starry orbs, would be shrouded in the deepest darkness, and the variegated surface of the globe on which we dwell, would be almost unnoticed and unknown. Creation would disappear, a mysterious gloom would surround the mind of everyintelligence, all around would appear a dismal waste, and an undistinguished chaos. To whatever quarter we might turn, no form nor comeliness would be seen, and scarcely a trace of the perfections and agency of an All Wise and Almighty Being could be perceived throughout the universal gloom. In short, without the influence of light, no world could be inhabited, no animated being could subsist in the manner it now does, no knowledge could be acquired of the works of God, and happiness, even in the lowest degree, could scarcely be enjoyed by any organized intelligence.
We have never yet known what it is to live in a world deprived of this delightful visitant; for in the darkest night we enjoy a share of its beneficial agency, and even in the deepest dungeon its influence is not altogether unfelt.1The blind, indeed, do not directly enjoy the advantages of light, but its influence is reflected upon them, and their knowledge is promoted through the medium of those who enjoy the use of their visual organs. Were all the inhabitants of the world deprived of their eye-sight, neither knowledge nor happiness, such as we now possess, could possibly be enjoyed.
There is nothing which so strikingly displays the beneficial and enlivening effects of light, as the dawn of a mild morning after a night of darkness and tempest. All appears gloom and desolation, in our terrestrial abode, till a faint light begins to whiten the eastern horizon. Every succeedingmoment brings along with it something new and enlivening. The crescent of light towards the east, now expands its dimensions and rises upwards towards the cope of heaven; and objects, which a little before were immersed in the deepest gloom, begin to be clearly distinguished. At length the sun arises, and all nature is animated by his appearance; the magnificent scene of creation, which a little before was involved in obscurity, opens gradually to view, and every object around excites sentiments of wonder, delight, and adoration. The radiance which emanates from this luminary, displays before us a world strewed with blessings and embellished with the most beautiful attire. It unveils the lofty mountains and the forests with which they are crowned—the fruitful fields with the crops that cover them—the meadows, with the rivers which water and refresh them—the plains adorned with verdure, the placid lake and the expansive ocean. It removes the curtain of darkness from the abodes of men, and shows us the cities, towns and villages, the lofty domes, the glittering spires, and the palaces and temples with which the landscape is adorned. The flowers expand their buds and put forth their colours, the birds awake to melody, man goes forth to his labour, the sounds of human voices are heard, and all appears life and activity, as if a new world had emerged from the darkness of Chaos.
The whole of this splendid scene, which light produces, may be considered as a new creation, no less grand and beneficent than the first creation, when the command was issued, “Let there be light, and light was.” The aurora and the rising sun cause the earth and all the objects which adorn its surface, to arise out of that profounddarkness and apparent desolation which deprived us of the view of them, as if they had been no more. It may be affirmed, in full accordance with truth, that the efflux of light in the dawn of the morning, after a dark and cloudy night, is even more magnificent and exhilarating than at the first moment of its creation. At that period, there were no spectators on earth to admire its glorious effects; and no objects, such as we now behold, to be embellished with its radiance. The earth was a shapeless chaos, where no beauty or order could be perceived; the mountains had not reared their heads; the seas were not collected into their channels; no rivers rolled through the valleys, no verdure adorned the plains; the atmosphere was not raised on high to reflect the radiance, and no animated beings existed to diversify and enliven the scene. But now, when the dawning of the morning scatters the darkness of the night, it opens to view a scene of beauty and magnificence. The heavens are adorned with azure, the clouds are tinged with the most lively colours, the mountains and plains are clothed with verdure, and the whole of this lower creation stands forth arrayed with diversified scenes of beneficence and grandeur, while the contemplative eye looks round and wonders.
Such, then, are the important and beneficent effects of thatlightwhich every moment diffuses its blessings around us. It may justly be considered as one of the most essential substances connected with the system of the material universe, and which gives efficiency to all the other principles and arrangements of nature. Hence we are informed, in the sacred history, that light was the first production of the Almighty Creator, and the first born of created beings; for without it theuniverse would have presented nothing but an immense blank to all sentient existences. Hence, likewise, the Divine Being is metaphorically represented under the idea of light, as being the source of knowledge and felicity to all subordinate intelligences: “God islight, and in Him is no darkness at all;” and he is exhibited as “dwelling in light unapproachable and full of glory, whom no man hath seen or can see.” In allusion to these circumstances, Milton, in his Paradise Lost, introduces the following beautiful apostrophe:—