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Page 19
We have been placed on the outside of this earth, instead of the
inside, in order that we may look abroad. We are carried about,
through unappreciable distance, at the inconceivable velocity of
one thousand miles a minute, to give us different points of vision.
The earth, on its softly-spinning axle, never jars enough to unnest
a bird or wake a child; hence the foundations of our observatories
are firm, and our measurements exact. Whoever studies astronomy,
under proper guidance and in the right spirit, grows in thought
and feeling, and becomes more appreciative of the Creator.
_Celestial Movements._
Let it not be supposed that a mastery of mathematics and a finished
education are necessary to understand the results of astronomical
research. It took at first the highest power of mind to make the
discoveries that are now laid at the feet of the lowliest. It took
sublime faith, courage, and the results of ages of experience in
navigation, to enable Columbus to discover that path to the New
World which now any little boat can follow. Ages of experience
and genius are stored up in a locomotive, but quite an unlettered
man can drive it. It is the work of genius to render difficult
matters plain, abstruse thoughts clear.
[Illustration: Fig. 19.]
A brief explanation of a few terms will make the principles of
world inspection easily understood. Imagine a perfect circle thirty
feet in diameter--that is, create [Page 59] one (Fig. 19). Draw
through it a diameter horizontally, another perpendicularly. The
angles made by the intersecting lines are each said to be ninety
degrees, marked thus �. The arc of a circle included between any two
of the lines is also 90�. Every circle, great or small, is divided
into these 360�. If the sun rose in the east and came to the zenith
at noon, it would have passed 90�. When it set in the west it would
have traversed half the circle, or 180�. In Fig. 20 the angle of the
lines measured on the graduated arc is 10�. The mountain is 10�
high, the world 10� in diameter, the comet moves 10� a day, the
stars are 10� apart. The height of the mountain, the diameter of the
world, the velocity of the comet, and the distance between the
stars, depend on the distance of each from the point of sight. Every
degree is divided into 60 minutes (marked '), and every minute into
60 seconds (marked ").
[Illustration: Fig. 20.--Illustration of Angles.]
Imagine yourself inside a perfect sphere one hundred feet in diameter,
with the interior surface above, around, and below studded with
fixed bright points like stars. The familiar constellations of
night might be blazoned there in due proportion.
If this star-sprent sphere were made to revolve once in twenty-four
hours, all the stars would successively [Page 60] pass in review.
How easily we could measure distances between stars, from a certain
fixed meridian, or the equator! How easily we could tell when any
particular star would culminate! It is as easy to take all these
measurements when our earthly observatory is steadily revolved
within the sphere of circumambient stars. Stars can be mapped as
readily as the streets of a great city. Looking down on it in the
night, one could trace the lines of lighted streets, and judge
something of its extent and regularity. But the few lamps of evening
would suggest little of the greatness of the public buildings, the
magnificent enterprise and commerce of its citizens, or the
intelligence of its scholars. Looking up to the lamps of the
celestial city, one can judge something of its extent and
regularity; but they suggest little of the magnificence of the many
mansions.
Stars are reckoned as so many degrees, minutes, and seconds from
each other, from the zenith, or from a given meridian, or from the
equator. Thus the stars called the Pointers, in the Great Bear,
are 5� apart; the nearest one is 29� from the Pole Star, which is
39� 56' 29" above the horizon at Philadelphia. In going to England
you creep up toward the north end of the earth, till the Pole Star
is 54� high. It stays near its place among the stars continually,
"Of whose true-fixed and resting quality
There is no fellow in the firmament."
_How to Measure._
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