reans, etc.-believed that they were celestial fires kept alive by matter that constantly streamed up to them from the centre of the heavens. The stars were at one time said to feed on air; at another, to be the breathing holes of the universe.

THREE ZONES OF STARS.-If we recall what was said

on page 104, concerning the paths of the stars and appearance of the heavens at different seasons of the year, we shall see that the constellations are naturally divided into three zones. The first embraces those which are visible through the entire year; the second, those whose orbits can be seen only in part on any given night; and the third, those whose paths just graze our southern horizon, or never pass above it.

THE CONSTELLATIONS.

NORTHERN CIRCUMPOLAR CONSTELLATIONS.-These constellations in our latitude are visible every night. They may be easily traced by holding the book up toward the northern sky in such a way that Polaris and the Dipper on the map and in the heavens agree in position, and then locating the other constellations by comparison. As they revolve about Polaris, their places will vary with every successive night through the year. The cut represents them as they are seen at midnight of the winter solstice. At 6 P. M. of that day the right-hand side of the map should be held downward, and the

Big Dipper will be directly below the north star. At 6 A. M. the left-hand side should be at the bottom, and the Dipper will be above Polaris.

day to day this aspect will change, each star coming

From

NORTHERN CIRCUMPOLAR CONSTELLATIONS

a little earlier to the meridian, or to its position on the preceding night. The rate of this progression is six hours, or 90°, in three months.

Ursa Major is represented under the figure of a great bear. It contains 138 stars visible to the naked eye. The constellation has been celebrated

1

among all nations. It is remarkable that the shepherds of Chaldea in Asia, and the Iroquois Indians of America, gave to it the same name.

Principal stars.-A noticeable cluster of seven stars-six of the second and one of the fourth magnitude-forms what is familiarly termed "The Dipper." In England it is styled Charles's Wain, from a fancied resemblance to a wagon drawn by three horses tandem. Mizar () has a minute companion, Alcor, which Humboldt tells us could be rarely seen in Europe. A person with good eyesight may now readily detect it. Megrez (d), at the junction of the handle and the bowl, is to be marked particularly, since it lies almost exactly in the colure passing through the autumnal equinox. Dubhe and Merak are termed "The Pointers," since they always point out the polar star. The bear's right fore paw and hinder paw are each marked by two small stars, as shown in the cut; a similar pair nearly in line with these denote the left hinder paw (see, Fig. 76). The pairs are 15° apart.

Mythological history.-Diana had a very beautiful attendant named Callisto. Juno, the queen of heaven, becoming jealous of the maid, transformed her into a bear.

"The prostrate wretch lifts up her head in prayer,
Her arms grow shaggy, and deformed with hair;
Her nails are sharpened into pointed claws,
Her hands bear half her weight and turn to paws.
Her lips, that once would tempt a god, begin
To grow distorted in an ugly grin.

And lest the supplicating brute might reach
The ears of Jove, she was deprived of speech.
How did she fear to lodge in woods alone,
And haunt the fields and meadows once her own!
How often would the deep-mouthed dogs pursue,
Whilst from her hounds the frighted hunters flew.

Some time afterward, Callisto's son, Arcas, being out hunting, pursued his mother and was about to transfix her with his uplifted spear, when Jupiter in pity transferred them both to the heavens, and placed them among the constellations as Ursa Major and Ursa Minor.

Ursa Minor is represented under the figure of a small bear. It contains twenty-four stars, of which only three are of the third, and four of the fourth magnitude.

Principal stars.-A cluster of seven stars forms what is termed the "Little Dipper." Three of them are small, and are seen with difficulty. Polaris, at the extremity of the handle, has been known from time immemorial as the North Polar Star. Among the Greeks it was styled Cynosure. Until the mariner's compass came into use, it was the star

"Whose faithful beams conduct the wandering ship
Through the wide desert of the pathless deep."

Polaris does not mark the exact position of the pole, since that is about 11° toward the Pointers. This distance will gradually diminish, until in time it will be only 10: then it will increase again, until in the lapse of ages-12,000 years hence-the bril

liant star a Lyra will fulfil the office of polar star for those who shall then live on the earth.

Curious fact concerning the Pyramids. Of the nine Pyramids which are standing at Gizeh, Egypt, six have openings facing the north. These lead to straight passages which descend at a uniform angle of about 26° and are parallel with the meridian. If we suppose a person, 4000 years ago, standing at the lower end of one of these passages, and looking out, his eye would strike the sky near the star Thuban, which was then the polar star. The supposed date of the building of these Pyramids (2123 B. C.) agrees with that epoch, and very naturally suggests that the builders had some special design in this peculiar construction.

The distance of Polaris is so great, that though the star is moving through space at the rate of ninety miles per minute, this tremendous speed is imperceptible to us. It requires nearly fifty years for its light to reach the earth; so that when we look at Polaris, we know that the ray which strikes our eye set out on its journey through space half a century ago. We cannot state positively that the star is now in existence, since if it were destroyed to-day it would be fifty years before we should miss it.

Calculation of latitude from Polaris.-By an observer at the equator, Polaris is seen at the horizon. If he advances north, the horizon is depressed and Polaris seems to rise in the heavens. When it has reached the height of a degree, the ob