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According to the Nautical Almanac, the mean distance of this star from the true pole of the heavens, for the year 1833 is 1° 34' 53', and its mean right ascension is 1 hour and 19 seconds. Consequently, when the right ascension of the meridian of any place is 1 hour and 19 seconds, the star will be exactly on the meridian at that time and place, but 1° 34' 53 above the true pole. Six hours after, when the right ascension of the meridian is 7 hours and 19 seconds, the star will be at its greatest elongation, or 1° 34' 53'' directly west of the true pole, and parallel to it, with respect to the horizon; and when the right ascension of the meridian is 13 hours and 19 seconds, the star will be again on the meridian, but at the distance of 1° 34' 53" directly below the pole.

In like manner, when the right ascension of the meridan is 19 hours and 19 seconds, the star will be at its greatest eastern elongation, or 1° 34′ 53'' east of the true pole; and when it has finished its revolution, and the right ascension of the meridian is 25 hours and 19 seconds, or, what is the same thing, 1 hour and 19 seconds, the star will now be on the meridian again, 1° 34' 53" above the pole.

N. B. The right ascension of the meridian or of the mid-heaven, is the distance of the first point of Aries from the meridian, at the time and place of observation. The right ascension of the meridian for any time, is found, by adding to the given time the sun's right ascension at the same time, and deducting 24 hours, when the sum exceeds 24 hours.

From the foregoing facts we learn, that from the time the star is on the meridian, above the pole, it deviates farther and farther from the true meridian, every hour, as it moves to the west, for the space of six hours, when it arrives at its greatest elongation west, whence it reapproaches the same meridian below the pole, during the next six hours, and is then again on the meridian; being thus alternately half the time west of the meridian, and half the time east of it.

Hence, it is evident that the surveyor who regulates his compass by the North Polar Star, must take his observation when the star is on the meridian, either above or below the pole, or make allowance for its altered position in every other situation. For the same reason must the navigator, who applies his quadrant to this star for the purpose of determining the latitude he is in, make a similar allowance, according as its altitude is greater or less than the true pole of the hea

What is the present distance of this star from the true pole of the heavens? What is its mean right ascension? When is it on the meridian, and what then is its bearing from the pole. What is its situation six hours afterwards? What is its situation six hours after that? What is its situation when in its third quadrant? What do you understand by the right ascension of the meridian, or of the mid-heaven? How do you find the right ascension of the mid-heaven? In what manner does the north star deviate from the meridian during one revolution? How do these facts concern the surveyor?

vens; for we have seen that it is alternately half the time above and half the time below the pole.

The method of finding the latitude of a place from the altıtude of the polar star, as it is very simple, is very often resorted to. Indeed, in northern latitudes, the situation of this star is more favourable for this purpose than that of any other of the heavenly bodies, because a single observation, taken at any hour of the night, with a good instrument, will give the true latitude, without any calculation or correction, except that of its polar aberration.

If the polar star always occupied that point in the heavens which is directly opposite the north pole of the earth, it would be easy to understand how latitude could be determined from it in the northern hemisphere; for in this case, to a person on the equator, the poles of the world would be seen in the horizon. Consequently, the star would appear just visible in the northern horizon, without any elevation. Should the person now travel one degree towards the north, he would see one degree below the star, and he would think it had risen one degree.

And since we always see the whole of the upper hemisphere at one view, when there is nothing in the horizon to obstruct our vision, it follows that if we should travel 10° north of the equator, we should see just 10° below the pole, which would then appear to have risen 10°; and should we stop at the 42d degree of north latitude we should, in like manner, have our horizon just 42° below the pole, or the pole would appear to have an elevation of 42°. Whence we derive this general truth: The elevation of the pole of the equator, is always equal to the latitude of the place of observation.

Any instrument, then, which will give us the altitude of the north pole, will give us also the latitude of the place.

The method of illustrating this phenomenon, as given in most treatises on the globe, and as adopted by teachers generally, is to tell the scholar that the north pole rises higher and higher, as he travels farther and farther towards it. In other words, whatever number of degrees he advances towards the north pole, so many degrees will it rise above his horizon. This is not only an obvious errour in principle, but it misleads the apprehension of the pupil. It is not that the pole is elevated, but that our horizon is depressed as we advance towards the north. The same objection lies against the artificial globe; for it ought to be so fixed that the horizon might be raised or depressed, and the pole remain in its own invariable position.

Ursa Minor contains twenty-four stars, including three of the 3d magnitude and four of the 4th. The seven principal stars are so situated as to form a figure very much resembling that in the Great Bear, only that the Dipper is reversed, and about one half as large as the one in that constellation.

The first star in the handle, called Cynosura, or Alruccabah, is the polar star, around which the rest constantly revolve. The two last in the bowl of the Dipper, corresponding to the Pointers in the Great Bear, are of the 3d magnitude,

Why is the method of finding the latitude by the polar star, often resorted to? Why is the position of this star favourable to this purpose? If the north star perfectly coincided with the north pole of the heavens, where would it be seen from the equator? Should a person travel one degree north of the equator, where would the star appear then? Suppose he should travel 10 degrees north of the equator? Suppose he were to stop at the 42d degree of north latitude? What general truth results from these facts? What, then, is all we want, to find the latitude of any place? Of what advantage to a mariner, is an instrument which will give the altitude of the pole? What are the number and magnitude of the stars, contained in Ursa Minor? What figure do the seven principal stars form? Describe the first in the handle of the Little Dipper. Describe the two last in the bowl of the Dipper.

and situated about 150 from the pole. The brightest of them is called Kochab, which signifies an axle or hinge, probably in reference to its moving so near the axis of the earth.

Kochab may be easily known by its being the brightest and middle one of three conspicuous stars forming a row, one of which is about 2°, and the other 3°, from Kochab. The two brightest of these are situated in the breast and shoulder of the animal, about 3° apart, and are called the Guards or Pointers of Ursa Minor. They are on the meridian about the 20th of June, but may be seen at all hours of the night, when the sky is clear.

Of the four stars which form the bowl of the Dipper, one is so small as hardly to be seen. They lie in a direction towards Gamma in Cepheus; but as they are continually changing their position in the heavens, they may be much better traced out from the map, than from description.

Kochab is about 25° distant from Benetnasch, and about 24° from Dubhe, and hence forms with them a very nearly equilateral triangle.

"The Lesser Bear

Leads from the pole the lucid band: the stars
Which form this constellation, faintly shine,
Twice twelve in number; only one beams forth
Conspicuous in high splendour, named by Greece
The Cynosure; by us the POLAR STAR."

HISTORY.-The prevailing opinion is, that Ursa Major and Ursa Minor are the nymph Calisto and her son Arcas, and that they were transformed into bears by the enraged and imperious Juno, and afterwards translated to heaven by the favour of Jupiter, lest they might be destroyed by the huntsmen.

The Chinese claim that the emperor Hong-ti, the grandson of Noah, first discovered the polar star, and applied it to purposes of navigation. It is certain that it was used for this purpose in a very remote period of antiquity. From various passages in the ancients, it is manifest that the Phoenicians steered by Cynosura, or the Lesser Bear; whereas the mariners of Greece, and some other nations, steered by the Greater Bear, called Helice, or Helix.

Lucan, a Latin poet, who flourished about the time of the birth of our Saviour, thus adverts to the practice of steering vessels by Cynosura :

"Unstable Tyre now knit to firmer ground,
With Sidon for her purple shells renown'd,
Safe in the Cynosure their glittering guide
With well-directed navies stem the tide."

Rowe's Translation, B. iii.

The following extracts from other poets contain allusions to the same fact:~,
"Phoenicia, spurning Asia's bounding strand,
By the bright Pole star's steady radiance led,
Bade to the winds her daring sails expand,
And fearless plough'd old Ocean's stormy bed."

MAURICE'S Elegy on Sir W. Jones.

"Ye radiant signs, who from the etherial plain
Sidonians guide, and Greeks upon the main,
Who from your poles all earthly things explore,
And never set beneath the western shore."

OVID'S Tristia.

How may Kochab be easily known? What are the position and name of the two brightest of these? When are they on the meridian? How is Kochab situated with respect to Benetnasch and Dubhe?

"Of all yon multitude of golden stars,

Which the wide rounding sphere incessant bears,
The cautious mariner relies on none,

But keeps him to the constant pole alone."

LUCAN'S Pharsalia, B. viii. v. 225.

Ursa Major and Ursa Minor, are sometimes called Triones, and sometimes the Greater and Lesser Wains. In Pennington's Memoirs of the learned Mrs. Carter, we have the following beautiful lines:

"Here, Cassiopeia fills a lucid throne,

There, blaze the splendours of the Northern Crown⚫
While the slow Car, the cold Triones roll

O'er the pale countries of the frozen pole:

Whose faithful beams conduct the wand'ring ship
Through the wide desert of the pathless deep."

Thales, an eminent geometrician and astronomer, and one of the seven wise men of Greece, who flourished six hundred years before the Christian era, is generally reputed to be the inventor of this constellation, and to. have taught the use of it to the Phoenician navigators; it is certain that he brought the knowledge of it with him from Phonice into Greece, with many other discoveries both in astronomy and mathematics.

Until the properties of the magnet were known and applied to the use of navi gation, and for a long time after, the north polar star was the only sure guide. At what time the attractive powers of the magnet were first known, is not cer tain; they were known in Europe about six hundred years before the Christian era; and by the Chinese records, it is said that its polar attraction was known in that country at least one thousand years earlier.

CHAPTER IX.

DIRECTIONS FOR TRACING THE CONSTELLATIONS WHICH ARE ON THE MERIDIAN IN JULY.

SCORPIO.

THE SCORPION.-This is the eighth sign, and ninth constellation, in the order of the Zodiac. It presents one of the most interesting groups of stars for the pupil to trace out that is to be found in the southern hemisphere. It is situated southward and eastward of Libra, and is on the meridian the 10th of July.

The sun enters this sign on the 23d of October, but does not reach the constellation before the 20th of November. When astronoiny was first cultivated in the East, the two solstices and the two equinoxes took place when the sun was in Aquarius and Leo, Taurus and Scorpio, respectively.

Scorpio contains, according to Flamsted, forty-four stars, including one of the 1st magnitude, one of the 2d, and eleven of the 3d. It is readily distinguished from all others by the peculiar lustre and the position of its principal stars.

Antares, is the principal star, and is situated in the heart

What is the position of Scorpio, among the signs and constellations of the Zodiac? How is it situated with respect to Libra, and when is it on our meridian? What are the number and magnitude of its stars? How is it readily distinguished from all others? Describe the principal star in this constellation}

of the Scorpion, about 19° east of Zubenelgubi, the southernmost star in the Balance. Antares is the most brilliant star in that region of the skies, and may be otherwise distinguished by its remarkably red appearance. Its declination is about 26° S. It comes to the meridian about three hours after Spica Virginis, or fifty minutes after Corona Borealis, on the 10th of July. It is one of the stars from which the moon's distance is reckoned for computing the longitude at sea.

There are four great stars in the heavens, Fomalhaut, Aldebaran, Regulus, and Antares, which formerly answered to the solstitial and equinoctial points; and which were much noticed by the astronomers of the East.

About 80 northwest of Antares, is a star of the 2d magnitude, in the head of the Scorpion, called Graffias. It is but one degree north of the earth's orbit. It may be recognised by means of a small star, situated about a degree northeast of it, and also by its forming a slight curve with two other stars of the 3d magnitude, situated below it, each about 30 apart. The broad part of the constellation near Graffias, is powdered with numerous small stars, converging down to a point at Antares, and resembling in figure a boy's kite.

As you proceed from Antares, there are ten conspicuous stars, chiefly of the 3d magnitude, which mark the tail of the kite, extending down, first in a south, southeasterly direction, about 170, thence easterly about 8° further, when they turn, and advance about 8° towards the north, forming a curve like a shepherd's crook, or the bottom part of the letter S. This crooked line of stars, forming the tail of the Scorpion, is very conspicuous, and may be easily traced.

The first star below Antares, which is the last in the back, is of only the 4th magnitude. It is about 20 southeast of Antares, and is denoted by the Greek name of T.

Epsilon, of the 3d magnitude, is the second star from Antares, and the first in the tail. It is situated about 70 below the star T, but inclining a little to the east. Mu, of the 3d magnitude, is the third star from Antares. It is situated 43° below Epsilon. It may otherwise be known by means of a sinall star close by it. on the left.

Zeta, of about the same magnitude, and situated about as far below Mu, is the fourth star from Antares. Here the line turns suddenly to the east.

Eta, also of the 3d magnitude. is the fifth star from Antares, and about 310 east of Zeta.

Theta, of the same magnitude, is the sixth star from Antares, and about 41° east of Eta. Here, the line turns again, curving to the north, and terminates in a couple of stars.

Iota, is the seventh star from Antares, 310 above Theta, curving a little to the left. It is a star of the 3d magnitude, and may be known by means of a small star, almost touching it, on the east.

Kappa, a star of equal brightness, is less than 20 above Iota, and a little to the right.

How is Antares otherwise distinguished? What is its declination? What is the time of its passing the meridian? What nautical importance is attached to its position? Describe Graffias? How may it be recognised? What is the appearance of the constellation between Graffias and Antares? How many conspicuous stars below Antares? What are their magnitude and general direction? Describe the first star below Antares. Describe the second star below Antares. Describe the third star, and tell how it may be known. Deseribe the fourth. Describe the fifth. Describe Theta. Describe Iota. Describe Kappa.

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