The Circle of Knowledge: A Classified, Simplified, Visualized Book of Answers

Chapter II: English and American Literature -- Outline Charts of English and (2)

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About half-way between Aries and γ Andromedæ are three stars which form a small triangle. This constellation is called Triangulum, or the Triangle.

Between Aries and Pegasus is the constellation Pisces, or the Fishes. The southernmost Fish may be recognized by a pentagon of small stars lying below the back of Pegasus. There are no conspicuous stars in the other Fish, which is directly below Andromeda.

CONSTELLATIONS VISIBLE IN NOVEMBER. At eight o’clock in the evening on the 15th of November, we see at a glance that the constellations with which we have become acquainted have moved yet farther to the westward. Boötes, the Crown, Ophiuchus, and the Archer have set; Pegasus, Cassiopeia, and Andromeda are overhead; while new constellations appear in the east.

We notice at once (Plate 11) a very bright star in the northeast, directly below Perseus. This is Capella, or α Aurigæ. There are five other conspicuous stars in Auriga, or the Charioteer; and with Capella they form an irregular pentagon.

Somewhat to the eastward (Plate 12), and a little lower down, is a very bright red star. This is Aldebaran, or α Tauri. It is familiarly known as the Bull’s eye. It will be noticed by the map that it is at one end of a V which forms the face of the Bull. This group is known as the Hyades. Somewhat above the Hyades is a smaller group, called the Pleiades,--more commonly known as the Seven Stars, though few persons can distinguish more than six. The bright star on the northern horn, or β Tauri, is also in the foot of Auriga, and counts as γ of that constellation.

All the space between Taurus and the Southern Fish, and below Aries and Pisces (Plate 13), is occupied by Cetus, the Whale. The head is marked by a triangle of rather conspicuous stars below Aries; the tail, by a bright star of the second magnitude, which is now just about as far above the horizon as Fomalhaut. On the body there are five stars, forming a sort of sickle. About halfway between this sickle and the triangle, in the head, is σ Ceti, which is also called Mira, or the wonderful star.

CONSTELLATIONS VISIBLE IN DECEMBER. At eight o’clock in the evening in the middle of December, we shall find that Hercules, Aquila, and Capricornus have sunk below the horizon; while Vega and the Swan are on the point of setting. The Great Bear is climbing up in the northeast. In the east we behold by far the most brilliant group of constellations we have yet seen. Capella and Aldebaran are now high up; and below the former (Plate 12) is the splendid constellation of Orion. His belt, made up of three stars in a straight line, will be recognized at once. Above this, on one shoulder, is a star of the first magnitude, called Betelgeuse, or α Orionis. About as far from the belt, on the other side, is another star of the first magnitude, called Rigel. There are two other fainter stars which form a large trapezium with Betelgeuse and Rigel. The three small stars below the belt are upon the sword.

Below Orion (Plate 14) is a small trapezium of stars which are in the constellation of Lepus, or the Hare. The head is marked by a small triangle, as seen on the map.

To the north of Orion, and a little lower down (Plate 12), are two bright stars near together, one of the first and the other of the second magnitude. The latter is called Castor, and the former Pollux. These stars are in the constellation of Gemini, or the Twins. A line of three smaller stars just in the edge of the Milky Way marks the feet, and another line of three the knees. Pollux forms a large triangle with Capella and Betelgeuse.

CONSTELLATIONS VISIBLE IN JANUARY. At eight in the evening on the 15th of January, Vega, Altair, the Dolphin, Aquarius, and Fomalhaut have disappeared in the west; Deneb and the Square of Pegasus are near the horizon; while Capella and Aldebaran are nearly overhead. Two stars of exceeding brilliancy have come up in the west. The one farthest to the south (Plate 14) is the brightest star in the whole heavens. It is called Sirius, or the Dogstar; and is in the constellation of Canis Major, or the Great Dog, which can be readily traced by the lines on the map.

The other bright star is between Sirius and Pollux (Plate 12), and is called Procyon. It is in Canis Minor, or the Little Dog. The only other prominent star in this constellation is one of the third magnitude near Procyon.

Procyon, Sirius, and Betelgeuse form a large equilateral triangle.

Orion and the group of constellations about it constitute by far the most brilliant portion of the heavens, as seen in our latitude. There are, in all, only about twenty stars of the first magnitude, and seven of these are in this immediate vicinity.

CONSTELLATIONS VISIBLE IN FEBRUARY. If we look at the heavens at the same time in the evening about the middle of February, we shall miss Cygnus and Pegasus from the west. Auriga and Orion are nearly overhead.

Southeast of the Great Bear (Plate 15) is a red star of the first magnitude, called Regulus, in the constellation of Leo, or the Lion. There are five stars near Regulus, which together with it form a group often called the Sickle. The star in the tail is Denebola, which makes a right-angled triangle with two others near it.

Between Leo and Gemini is the constellation Cancer, or the Crab. It contains no bright stars, but a remarkable cluster of small stars called Præsepe, or the Beehive.

Below Regulus (Plate 14) is a bright red star of the second magnitude, called Cor Hydræ, or the Hydra’s Heart. The head of Hydra is marked by five small stars. The coils of the monster can be traced by the map. A portion of the constellation is on Plate 16.

CONSTELLATIONS VISIBLE IN MARCH. At the middle of March, the heavens will have shifted round somewhat towards the west; but all the conspicuous constellations of the preceding month are still visible, while no new ones at all brilliant have come into view.

If we draw a line from the end of the Great Bear’s tail to Denebola, it will pass through two constellations,--Canes Venatici, described above; and Coma Berenices, or Berenice’s Hair, a large cluster of faint stars. (Plate 15).

1. Double nebula in Gemini. 2. Double nebula of great brilliancy in Coma Berenicis. 3. Small double nebula. 4. Curiously shaped nebula in Ophiuchus. 5. Two nebulous spots in Canes Venatici. 6. Remarkable veil-like nebula in Lyra. 7. Elliptical nebula in Perseus. 8. Nebulous spot in Sagittarius, split into three pieces; a double star in center. 9. Large curiously-shaped nebula in Rober Caroli, filled with minute stars. 10. Great nebula in Andromeda, visible to the eye. 11. Nebula in Cetus. 12. Elongated nebula in Cygnus. 13. Brilliant round spots in Sagittarius. 14. Round spots in Andromeda. 15-16. Spots in Orion and Ursa Major. 17. Most remarkable of all nebula, in Orion. 18. Great oval nebula in Vulpes, containing two darker nebulae. 19. Nebulous figure in Canis Venaticus. 20. Nebular clouds in the Southern hemisphere.]

CONSTELLATIONS VISIBLE IN APRIL. At the middle of April, Aries and Andromeda have set; Taurus, Orion and Canis Major are sinking towards the west; the Great Bear and the Lion are overhead; Arcturus has risen in the northeast (Plate 16); and some way to the south of this is seen a star of the first magnitude, which forms a large triangle with Arcturus and Denebola. It is called Spica Virginis, and is the chief star in the constellation Virgo, or the Virgin. The stars on the breast and wings can be found with the aid of the map.

South of Virgo is a trapezium of four stars, which are in the constellation of Corvus, or the Crow.

CONSTELLATIONS VISIBLE IN MAY. At the middle of May, Taurus, Orion, and Canis Major have set; Vega has just come up in the northeast; and between Vega and Arcturus we again see Hercules and Corona. Below Spica are two stars of the second magnitude, belonging to the constellation Libra, or the Balance. Another star of the fourth magnitude forms a triangle with these, and marks one pan of the balance. (Plate 7).

CONSTELLATIONS VISIBLE IN JUNE. In June we shall find that Canis Minor, Perseus, Auriga, and Gemini have either set, or are on the point of setting; Arcturus is overhead; Cygnus and Aquila are just rising. Ophiuchus is well up; and low in the southeast we see again the red star Antares, in the constellation Scorpio, or the Scorpion (Plate 6). There is a star of the third magnitude on each side of Antares, and several stars of the third and fourth magnitudes in the head and claws. The configuration of these stars is much like a boy’s kite with a long tail. Scorpio is a very brilliant constellation, and is seen to better advantage in July and August.

CONSTELLATIONS VISIBLE IN JULY AND AUGUST. We have now described all the important constellations visible in our latitude. Those which are seen in July and August are mainly those described under the last two or three months, and under September.

SOUTHERN CIRCUMPOLAR CONSTELLATIONS. There are a number of constellations near the South Pole of the heavens which never rise in our latitude, just as there are certain ones near the North Pole which never set. These are called the southern circumpolar constellations.

=CONSTELLATIONS VISIBLE EACH MONTH=

The following table gives the constellations visible at eight
o’clock in the evening about the middle of each month. The stars
opposite the names of the constellations indicate those visible in
the month designated at the top.

+-------------------------------------------+-+-+-+-+-+-+-+-+-+-+-+-+
| |S|O|N|D|J|F|M|A|M|J|J|A|
| |e|c|o|e|a|e|a|p|a|u|u|u|
| NAME OF CONSTELLATION |p|t|v|c|n|b|r|r|y|n|l|g|
| |t|.|.|.|.|.|.|i| |e|y|.|
| |.| | | | | | |l| | | | |
+-------------------------------------------+-+-+-+-+-+-+-+-+-+-+-+-+
|=Ursa Major= (_er´sa mā´jor_). The Greater | | | | | | | | | | | | |
|Bear. |*|*|*|*|*|*|*|*|*|*|*|*|
|=Ursa Minor= (_er´sa mī´nor_). The Lesser | | | | | | | | | | | | |
|Bear. |*|*|*|*|*|*|*|*|*|*|*|*|
|=Draco= (_drak´ō_). Dragon. |*|*|*|*|*|*|*|*|*|*|*|*|
|=Cassiopeia= (_kas-si-o-pē´a_). Lady’s | | | | | | | | | | | | |
|Chair. |*|*|*|*|*|*|*|*|*|*|*|*|
|=Cepheus= (_sē´fe-us_). |*|*|*|*|*|*|*|*|*|*|*|*|
|=Bootes= (_bo-ō´tēz_). The Oxdriver or | | | | | | | | | | | | |
|Plowman. |*| | | | | | |*|*|*|*|*|
|=Corona Borealis= (_kō-rō´na bō-rē-ā´lis_).| | | | | | | | | | | | |
|The Northern Crown. |*|*| | | | | | |*|*|*|*|
|=Ophiuchus= (_of-i-u´kus_). The Serpent | | | | | | | | | | | | |
|Bearer. |*| | | | | | | | |*|*|*|
|=Sagittarius= (_saj-i-tā´ri-us_). The | | | | | | | | | | | | |
|Archer. |*| | | | | | | | | |*|*|
|=Hercules= (_her´ku-lēz_). |*|*| | | | | | |*|*|*|*|
|=Lyra= (_lī´ra_). The Lyre. |*|*|*| | | | | | |*|*|*|
|=Aquila= (_ak´wil-a_). |*|*|*| | | | | | | |*|*|
|=Delphinus= (_del´fin-us_). Dolphin. |*|*|*| | | | | | | |*|*|
|=Capricornus= (_kap-ri-kor´nus_). The Goat.|*|*|*| | | | | | | | |*|
|=Cygnus= (_sig´nus_). The Swan. |*|*|*|*| | | | | |*|*|*|
|=Sagitta= (_saj´it-ta_). The Arrow. |*|*|*| | | | | | | |*|*|
|=Aquarius= (_a-kwā´ri-us_). The Water- | | | | | | | | | | | | |
|bearer. |*|*|*|*| | | | | | | | |
|=Piscis Australis= (_pis´sis aw-strā´lis_).| | | | | | | | | | | | |
|The Southern Fish. |*|*|*|*| | | | | | | | |
|=Pegasus= (_peg´a-sus_). The Winged Horse. |*|*|*|*|*| | | | | | | |
|=Andromeda= (_an-drom´e-da_). |*|*|*|*|*|*|*| | | | | |
|=Perseus= (_per´sus_). |*|*|*|*|*|*|*|*| | | | |
|=Aries= (_a´ri-ēz_). Ram. | |*|*|*|*|*|*| | | | | |
|=Pisces= (_pis´sēz_). Fishes. | |*|*|*|*| | | | | | | |
|=Cetus= (_sē´tus_). The Whale. | | |*|*|*|*| | | | | | |
|=Triangulum= (_trī-ang´u-lum_). The | | | | | | | | | | | | |
|Triangle. | | |*|*|*|*|*| | | | | |
|=Auriga= (_aw-ri´ga_). The Waggoner or The | | | | | | | | | | | | |
|Charioteer. | | |*|*|*|*|*|*|*| | | |
|=Taurus= (_tau´rus_). The Bull. | | |*|*|*|*|*|*| | | | |
|=Lepus= (_lep´us_). The Hare. | | | |*|*|*|*| | | | | |
|=Orion= (_ō-ri´on_). Giant and Hunter. | | | |*|*|*|*|*| | | | |
|=Gemini= (_jem´i-ni_). The Twins. | | | |*|*|*|*|*|*| | | |
|=Canis Major= (_kā´nis mā´jor_). The Great | | | | | | | | | | | | |
|Dog. | | | | |*|*|*|*| | | | |
|=Canis Minor= (_kā´nis mī´nor_). The Little| | | | | | | | | | | | |
|Dog. | | | | |*|*|*|*|*| | | |
|=Cancer= (_kan´ser_). The Crab. | | | | | |*|*|*|*|*| | |
|=Hydra= (_hī´dra_). The Snake. | | | | | |*|*|*|*|*| | |
|=Leo= (_lē´ō_). The Lion. | | | | | |*|*|*|*|*|*| |
|=Coma Berenices= (_kō´ma ber-e-nī´sēz_). | | | | | | | | | | | | |
|Hair of Berenice. | | | | | | |*|*|*|*|*|*|
|=Canes Venatici= (_ka´nēz vē-nā´ti-si_). | | | | | | | | | | | | |
|The Hunter’s Dogs. | | | | | | |*|*|*|*|*|*|
|=Virgo= (_ver´gō_). The Virgin. | | | | | | | |*|*|*|*|*|
|=Corvus= (_kor´vus_). The crow. | | | | | | | |*|*|*|*| |
|=Libra= (_li´bra_). Balance. | | | | | | | |*|*|*|*| |
|=Scorpio= (_skor´pi-ō_). The Scorpion. | | | | | | | | | |*|*|*|
+-------------------------------------------+-+-+-+-+-+-+-+-+-+-+-+-+

THE WONDERFUL MILKY WAY

Everyone knows the Milky Way. It is one of the most striking sights of a clear night, for only on clear, moonless nights can we see its cloudy track of light across the heavens. More than any other celestial object it affects us with a sense of mystery and of unknown destiny as, indeed, it has affected men at all times and in all countries. To the American Indian it was the “path of souls.” In ancient mythology it had various meanings: thus, it was the highway of the gods to Olympus; or it sprang from the ears of corn dropped by Isis as she fled from her pursuer; or it marked the original course of the sun, which he later abandoned. In mediæval times it became associated by pilgrims with their own journeys.

It stretches like a vast ragged semicircle over the sky. Indeed, it traces a rough circle, for this line is continued over the southern hemisphere also. The circle is, however, very far from being smooth or even; the path is full of irregularities. It varies in width to an extent of about thirty degrees, and varies also considerably in brightness. Its total area has been estimated to cover rather less than one-fourth of the whole northern hemisphere of the sky, and to cover about one-third of the southern hemisphere. Its track lies through the constellations Cassiopeia and Auriga; it passes between the feet of Gemini and the horns of Taurus, through Orion just above the giant’s club, and through the neck and shoulder of Monoceros. It passes above Sirius into Argo, here entering the southern hemisphere, and through Argo and the Southern Cross into the Centaur. In the Centaur the Milky Way divides into two streams, in a manner which suggests the divided course of a river around an island, a dark rift between the two luminous streams representing the island.

It is a very long island, however, for the double conformation of the Milky Way extends over one-third of its entire course--that is to say, one hundred and twenty degrees of the circle. The divergent branches reunite in the northern hemisphere in the constellation Cygnus. The brighter stream passes through Norma, Ara, Scorpio and Sagittarius; along the bow of Sagittarius into Antinous, here entering the northern hemisphere again; then through Aquila, Sagitta, and Vulpecula it arrives at Cygnus and reunion with the branch which left it in Centaur. From Cygnus the stream, now single, passes through Lacerta and the head of Cepheus to the point whence we started, in Cassiopeia.

As we follow the Milky Way throughout its course, we find it continually sending out streaming appendages of nebulous appearance towards clusters, nebulæ, or groups of stars. In Norma it sends out a complicated series of nebulous streaks and patches, covering the Scorpion’s tail, spreading faintly over the leg of Ophiuchus, and extending beyond, as if to meet a corresponding branch sent off from the region of Cygnus in the northern hemisphere. The latter is a very bright and remarkable streak, running south through Cygnus and Aquila, to become lost in a dim and sparsely starred region. From Cassiopeia a vivid branch proceeds to the chief star of Perseus, and faint streaks appear to continue the “feeler” towards the Hyades and the Pleiades. There are many other “feelers” of the same kind, and they are all of great interest, because they seem to show some sort of influence exercised by the Milky Way upon the whole starry universe.

ANCIENT AND MODERN CONCEPTIONS OF THE NATURE OF THE MILKY WAY. Strange theories as to the nature of the Milky Way have been put forward at various times. Anaxagoras thought it might be due to the shadow of our globe; Aristotle, that it was some kind of mist due to the exhalation of vapors from the earth.

But a grander and truer conception of its nature and situation, removed far from the earth and independent of any terrestrial cause, had early come to several minds. Pythagoras and Democritus both formed the conjecture that its shimmer might be due to innumerable stars, and Galileo’s telescope confirmed their theory.

As we have seen, the Milky Way is by no means a simple stream of stars; with careful observation, even the naked eye can perceive something of its irregular detail, when the atmosphere is unusually clear, and there is no moon. Viewed under these conditions through a good telescope, the effect of the Milky Way, when made to pass progressively before the vision, is one of unexampled grandeur and sublimity.

=COURSE OF THE MILKY WAY THROUGH THE TWO HEMISPHERES OF THE HEAVENS=

These two drawings show the two semi-circles of the Milky Way as they extend from the regions of the Polar Star to the region of the Southern Cross on each side of the apparent sphere of the heavens. It will be noticed that the bright stars congregate near its region, and that there is a characteristic harmony in the way in which the wisps appear to project into space, suggesting some common cause for this appearance throughout the whole galaxy.]

The general effect has been well likened to that of an old, gnarled tree-trunk, marked with knots and curving lines, and riddled with dark holes and passages, linked together by shimmering wisps or arches. This general effect is practically lost as the detail becomes clear in a telescopic view. The detail is extremely various. At one point it may consist of separate stars scattered irregularly upon a background of darkness; at another, of star-clusters, sometimes following one upon another in long, processional line; at another, the stars seem to collect in small, soft clouds, presenting the appearance, as the telescope sweeps over them, of drifting foam.

THE STRANGE, DARK RIFTS IN THE SKYSCAPE WHERE NO STARS APPEAR. At yet another point the track may be involved in nebulosity in which many stars appear to be imbedded. Perhaps the most characteristic features are several which have already been remarked as conspicuous in star-clusters or nebulæ, such as lines of stars, dark lanes or rifts, and dark holes. The lines of stars, which are evidently connected by some actual physical relation, are either straight, curved, radiated, or in parallels. In Sagittarius is a very striking collection of about thirty stars resembling in form a forked twig with a curved hook at the unforked end. The dark rifts in the Milky Way show the same features as those in star-clusters. Sometimes they are parallel; sometimes they radiate like branches from a common center; sometimes they are lines with bright stars; sometimes they are quite black, as if utterly void; sometimes slightly luminous, as if powdered with small stars.

It can be by no accident or chance that in the vast edifice of the heavens objects of certain classes should crowd into the belt of the Milky Way, and other classes avoid it; it points to the whole forming a single growth, an essential unity. For there is but one belt in the heavens, like the Milky Way, a belt in which small stars, new stars, and planetary nebulæ find their favorite home; and that belt encircles the entire heavens; and similarly that belt is the only region from which the white nebulæ appear to be repelled. The Milky Way forms the foundation, the strong and buttressed wall of the celestial building; the white nebulæ close in the roof of its dome.

NEBULAE AND THE THEORY OF THE UNIVERSE

It has already been observed that a number of stars are arranged in clusters of groups, while others, like our own sun, are at vast distances from their nearest neighbors. Some of these clusters, of which the Pleiades afford the best example to the naked eye, can be resolved by a keen eye into separate stars; some, like Præsepe in Cancer, which only show to the naked eye as a hazy spot of light, break up in a good field-glass into clusters of stars; but the majority of stellar clusters require a powerful telescope for their resolution.

It was long ago noticed that, the more powerful a telescope was, the greater was the number of these hazy spots of light which it would resolve into clusters of stars. Consequently the opinion was formed that all the hazy little clouds or nebulæ which are so prevalent throughout a large part of the sky were simply clusters of stars, so far away that their light merged into a single impression on the eye. A great number of these nebulæ were only resolved by large telescopes; many were found to be irresolvable by any telescope. It was simply concluded from this that they were still more distant than the clusters which had yielded to the resolving powers of the telescope; and it was further supposed that each of these clusters of stars might be a separate universe or galaxy, comparable in extent and importance with our own universe, bounded by the vast girdle of the Milky Way.

THE NEBULAR HYPOTHESIS. This grand conception of innumerable universes scattered throughout space was speedily destroyed by the spectroscope, which distinguishes with entire certainty between the light sent to us from a solid star and that emitted by a gas. When it was turned upon the nebulæ which had been supposed in reality to be star-clusters so distant that no telescope could resolve them, it showed unmistakably that these nebulæ were not star-groups, but simply masses of incandescent gas.

Besides, nebulæ vary greatly in form and appearance; some are clearly clusters of stars, others are perfectly hazy. A round or oval form is sometimes exhibited, with a gradual condensation towards the center, and a number of stars standing in the center of a nebulous haze can be observed. Such observations on nebulæ caused Kant and Laplace to suggest a theory--now known as the nebular theory--as to the formation of worlds. They considered that the solar system, for example, originally existed as uncondensed nebulous matter. This gradually condensed towards the center, forming the nucleus of the sun, and later the outer parts separated into distinct parts, each part condensing into a planet. The different forms of nebulæ observed in the heavens are then supposed to be systems in different stages of development.

THE VARIED COLOR OF THE STARS

Many of the stars shine with colored light, as red, blue, green, or yellow.

These colors are exhibited in striking contrast in many of the double stars. Combinations of blue and yellow, or green and yellow, are not uncommon; while in fewer cases we find one star white and the other purple, or one white and the other red. In several instances each star has a rosy light.

The following are a few of the most interesting colored double stars:

Color of Color of Smaller
Name of Star Larger One One

γ Andromedæ Orange Sea-Green.
α Piscium Pale Green Blue.
β Cygni Yellow Sapphire Blue.
η Cassiopeiæ Yellow Purple.
σ Cassiopeiæ Greenish Bright Blue.
ζ Coronæ White Light Purple.
ι Cancri Orange Blue.
α Herculis Orange Emerald Green.

Single stars of a fiery red or deep orange color are common enough. Of the first color may be mentioned Aldebaran, Antares and Betelgeuse. Arcturus is a good example of an orange star. Isolated stars of a deep blue or green color are very rarely found; among the conspicuous stars, β Libræ appears to be the only instance.

It is now a well-established fact that the stars change their color. Sirius was described as a fiery red star by the ancients, is now decided green color.

=NAMES OF IMPORTANT STARS=

INCLUDING THOSE OF FIRST MAGNITUDE

Individual Constellation in
Name Meaning Which Found

Achernar The End of The River α Eridani.
Alcor The Near One 80 Ursæ Majoris.
Alcyone Daughter of Atlas and Pleione η Tauri.
Aldebaran The Follower α Tauri.
Algenib The Side γ Pegasi.
Algol The Demon Star β Persei.
Alioth The Tail (of the Sheep) ε Ursæ Majoris.
Altair The Soaring Eagle α Aquilæ.
Antares The Rival of Mars α Scorpii.
Arcturus The Watcher of the Bear α Boötis.
Bellatrix The Woman Warrior γ Orionis.
Betelgeux The Shoulder of the Giant α Orionis.
Canopus The Pilot of Menelaus α Argûs.
Capella The Goat α Aurigæ.
Caph The Hand β Cassiopeiæ.
Castor Son of Zeus and Leda α Geminorum.
Cor Caroli Charles’ Heart α Canum Ven.
Deneb The Tail α Cygni.
Denebola The Lion’s Tail β Leonis.
Dubhe The Bear α Ursæ Majoris.
Fomalhaut The Fish’s Mouth α Piscis Australis.
Markab The Saddle α Pegasi.
Mira Ceti The Wonderful Star of Cetus ο Ceti.
Mizar The Girdle ζ Ursæ Majoris.
Polaris The Pole Star α Ursæ Minoris.
Pollux Son of Zeus and Leda β Geminorum.
Procyon Before the Dog α Canis Minoris.
Regulus The Little King α Leonis.
Rigel The Foot β Orionis.
Sirius Chief α Canis Majoris.
Spica The Ear of Corn α Virginis.
Vega The Swooping Eagle α Lyræ.

WHAT CAUSES THE ECLIPSES

When the earth is between the moon and the sun in a line, the moon lies in the shadow of the earth, and so suffers temporary obscuration; a _lunar eclipse_ then takes place. When the moon passes between the earth and the sun, the latter is at certain places on the earth obscured by the dark body of the moon, and a _solar eclipse_ takes place.

LUNAR ECLIPSES. The shadow cast by the earth is conical, and may be shown to extend about one million miles from its surface. At a distance of a quarter of a million miles away the width of this shadow is about six thousand miles; and if the moon passes into it at that approximate distance from the earth, its disc of two thousand miles diameter may be partially or totally obscured. The moon and sun may be on opposite sides of the earth, and yet the former not in shadow. This is due to the fact that the moon’s orbit round the earth is not exactly in the same plane as that of the earth’s orbit round the sun. If it were so, we should have total eclipses at every full moon; but since the two planes are inclined to each other at an angle of 5° 9′, eclipses will occur when the moon is at or near its _nodes_ or positions of coincidence with the plane of the ecliptic. Partial eclipses are produced when only a portion of the moon passes into shadow; annular eclipses such as are sometimes observed in the case of the sun cannot occur with the moon.

=HOW THE MOON THROWS ITS SHADOW ON THE EARTH, SHUTTING OFF THE LIGHT OF THE SUN=]

On its way through space the moon passes sometimes between the sun and the earth, shutting off the sunlight from the earth, as shown in the top picture. The drawing in the middle shows us that the moon does not hide the sunlight from the whole of the earth, but only from a part of it. But in the part from which the sun is hid the moon’s shadow makes day so dark that we can see the stars. We call this an eclipse of the sun. Sometimes, too, the earth passes between the moon and the sun so as to cut off all sunlight from the moon, as shown in the bottom picture. We call this an eclipse of the moon.]

SOLAR ECLIPSES. The shadow cast by the moon is also conical, and extends over a slightly varying distance of about a quarter of a million miles from the moon’s surface. This being the approximate distance of the moon from the earth, it is seen that when the moon is between the earth and the sun the shadow may reach the earth. The extreme limit of the shadow may range from twenty-three thousand miles short of the earth, in which case an entire eclipse of the sun is impossible, to fifteen thousand miles beyond the earth. In the latter case a circular shadow will be projected on the surface of the globe, travelling onwards slowly in the direction of the motion of the moon. Within this shadow or _umbra_ the body of the sun cannot be observed, and a total eclipse prevails. A circular region exists round this shadow, in which only part of the sun is visible; this region is therefore partly in shadow, and is called the _penumbra_. Outside the penumbra the whole sun may be viewed; the moon’s shadow is not nearly large enough to render a solar eclipse co-existent over all parts of the earth’s face towards the sun.

THE MYTHOLOGY OF THE CONSTELLATIONS

To the Greeks the starry heavens were an illustrated mythological poem. Every constellation was a picture, connected with some old fable of gods or heroes.

The two Bears have one story. Callisto was a nymph beloved by Jupiter, who changed her into a she-bear to save her from the jealous wrath of Juno. But Juno learned the truth, and induced Diana to kill the bear in the chase. Jupiter then placed her among the stars as Ursa Major, and her son Arcas afterwards became Ursa Minor. Juno, indignant at the honor thus shown the objects of her hatred, persuaded Tethys and Oceanus to forbid the Bears to descend, like the other stars, into the sea.

According to Ovid, Juno changed Callisto into a bear; and when Arcas, in hunting, was about to kill his mother, Jupiter placed both among the stars.

Ursa Minor was also called Phœnice, because the Phœnicians made it their guide in navigation, while the Greeks preferred the Great Bear for that purpose. It was also known as Cynosura (dog’s tail) from its resemblance to the upturned curl of a dog’s tail. The Great Bear was sometimes called Helice (winding), either from its shape or its curved path.

Boötes (the Herdsman) was also called Arctophylax and Arcturus, both of which names mean the guard or keeper of the bear. According to some of the stories, Boötes was Arcas; according to others, he was Icarus, the unfortunate son of Dædalus. The name Arcturus was afterwards given to the chief star of the constellation.

Cepheus, Cassiopeia, Andromeda, Perseus, and Pegasus are a group of star-pictures illustrating a single story.

Cepheus and Cassiopeia were the king and queen of Ethiopia, and had a very beautiful daughter, Andromeda. Her mother boasted that the maiden was fairer than the Nereids, who in their anger persuaded Neptune to send a sea-monster to ravage the shores of Ethiopia. To appease the offended deities Andromeda, by the command of an oracle, was exposed to this monster. The hero Perseus rescued her and married her.

Pegasus, the winged horse, sprang from the blood of the frightful Gorgon, Medusa, whom Perseus had slain not long before he rescued Andromeda from the sea-monster. According to the most ancient account, Pegasus became the horse of Jupiter, for whom he carried the thunder and lightning; but he afterward came to be considered the horse of Aurora, and finally of the Muses. Modern poets rarely speak of him except as connected with the Muses.

The Dragon, according to some of the poets, was the one that guarded the golden apples of the Hesperides; according to others, the monster sacred to Mars which Cadmus killed in Bœotia.

The Lyre is said to be the one which Apollo gave to Orpheus. After the death of Orpheus, Jupiter placed it among the stars at the intercession of Apollo and the Muses.

The Crown was the bridal gift of Bacchus to Ariadne, transferred to the heavens after her death.

Aquila is probably the eagle into which Merops was changed. It was placed among the stars by Juno. Some, however, make it the Eagle of Jupiter.

Cygnus or Cycnus, according to Ovid, was a relative of Phaëthon. While lamenting the unhappy fate of his kinsman on the banks of the Eridanus, he was changed by Apollo into a swan, and placed among the stars.

Sagittarius was said by the Greeks to be the Centaur Cheiron, the instructor of Peleus, Achilles and Diomed. It is pretty certain, however, that all the zodiacal constellations are of Egyptian origin, and represent twelve Egyptian deities who presided over the months of the year. Thus Aries was Jupiter Ammon; Taurus, the bull Apis; Gemini, the inseparable gods Horus and Harpocrates; and so on. The Greeks adopted the figures, and invented stories of their own to explain them.

Scorpio, in the Egyptian zodiac, represented the monster Typhon. Originally this constellation extended also over the space now filled by Libra.

Ophiuchus represents Æsculpius, the god of medicine. Serpents were sacred to him, probably because they were a symbol of prudence and renovation, and were believed to have the power of discovering herbs of wondrous powers.

Aquarius, in Greek fable, was Ganymede, the Phrygian boy who became the cup-bearer of the gods in place of Hebe.

Taurus, as has been stated above, was the Egyptian Apis. The Greeks made it the bull which carried off Europa. The Pleiades are usually called the daughters of Atlas, whence their name Atlantides. Milton speaks of them as “the seven Atlantic Sisters.”

According to one legend the seventh was Sterope, who became invisible because she had loved a mortal; according to another, her name was Electra, and she left her place that she might not witness the downfall of Troy, which was founded by her son, Dardanus.

The Hyades, according to one of several stories, were sisters of the Pleiades. The name probably means “the Rainy,” since their rising announced wet weather.

Cetus is said by most writers to be the sea-monster from which Perseus rescued Andromeda.

Orion was a famous giant and hunter, who loved the daughter of Oinopion, King of Chios. As her father was slow to consent to her marriage, Orion attempted to carry off the maiden; whereupon Oinopion, with the help of Bacchus, put out his eyes. But the hero, in obedience to an oracle, exposed his eye-balls to the rays of the rising sun, and thus regained his sight. The accounts of his subsequent life, and of his death, are various and conflicting. According to some, Aurora loved him and carried him off; but, as the gods were angry at this, Diana killed him with an arrow. Others say that Diana loved him, and that Apollo, indignant at his sister’s affection for the hero, once pointed out a distant object on the surface of the sea, and challenged her to hit it. It was the head of Orion swimming, and the unerring shot of the goddess pierced it with a fatal wound. Another fable asserts that Orion boasted that he would conquer every animal; but the earth sent forth a scorpion which destroyed him.

Canis Major and Minor are the dogs of Orion, and are pursuing the Hare.

The Twins, Castor and Pollux, the sons of Jupiter and Leda, are the theme of many a fable. They were especially worshipped as the protectors of those who sailed the seas, for Neptune had rewarded their brotherly love by giving them power over winds and waves, that they might assist the shipwrecked.

Leo, according to the Greek story, was the famous Nemean lion slain by Hercules. Jupiter placed it in the heavens in honor of the exploit.

The Hydra also commemorates one of the twelve labors of Hercules--the destruction of the hundred-headed monster of the Lernæan lake.

Virgo represents Astræa, the goddess of innocence and purity, or, as some say, of justice. She was the last of the gods to withdraw from earth at the close of “the golden age.”

Libra, or the Balance, is the emblem of justice, and is usually associated with the fable of Astræa.

Argo Navis is the famous ship in which Jason and his companions sailed to find the Golden Fleece.

This slight sketch of the leading fables connected with the constellations will serve to show how completely the Greeks “nationalized the heavens.”

SCIENTIFIC TERMS USED IN ASTRONOMY

=Astronomy= (_as-tron´om-i_). The science which treats of the heavenly bodies, explaining the motions, times and causes of the motions, distances, magnitudes, gravities, light, etc., of the sun, moon, and stars, the nature and causes of the eclipses of the sun and moon, the conjunction and apposition of the planets, and any other of their mutual aspects, with the times when they did or will happen.

* * * * *

=Aberration= (_ab-er-ā´shun_). A small apparent motion of the fixed stars, occasioned by the progressive motion of light and the earth’s annual motion in its orbit. By this they sometimes appear twenty seconds distant from their true situation.

=Amplitude= (_am´pli-tud_). An arc of the horizon intercepted between the true east and west points and the center of the sun, or a star at its rising or setting.

=Anomaly= (_an-om´al-i_). The angular distance of a planet from its perihelion, as seen from the sun; either true, mean, or eccentric.

=Aphelion= (_af-ēl´yun_). That point of a planet’s orbit which is most distant from the sun.

=Apogee= (_ap´o-jē_). That point in the orbit of the moon which is at the greatest distance from the earth.

=Apparition= (_ap-par-ish´un_). The first appearance of a star or other luminary after having been obscured.

=Ap´pulse=. The approach of a planet towards a conjunction with the sun or any of the fixed stars.

=Apsis= (_ap´sis_). The two points of a planet’s orbit in which it is at its greatest and least distance from the sun.

=Aquarius= (_a-kwā´ri-us_). The eleventh sign of the zodiac, which the sun enters about the 21st of January.

=Asteroids= (_as´ter-oids_). The small planets that circulate between the orbits of Mars and Jupiter.

=Ax´is= (_ax´is_). The imaginary line passing through the center and poles of the earth, on which it performs its diurnal revolutions from west to east.

=Azimuth= (_az´im-uth_). An arc of the horizon intercepted between the meridian of the place and the vertical circle passing through the center of a celestial object.

=Can´cer=. The fourth sign of the zodiac, being that of the summer solstice, which the sun enters about the 21st of June.

=Capricorn= (_kap´ri-korn_). The tenth sign of the zodiac, which the sun enters about the 21st of December, at the winter solstice.

=Colure= (_kol´ur_). Two great circles, supposed to intersect each other at right angles in the poles of the world, one of them passing through the solstitial and the other through the equinoctial points of the ecliptic, viz., Cancer and Capricorn, Aries and Libra, dividing the ecliptic into four equal parts.

=Coma= (_kō´ma_). A dense, nebulous covering, which surround the nucleus or body of a comet.

=Com´et=. A member of the solar system, commonly consisting of three parts: the nucleus, the envelope or coma, and the tail; but one or more of these parts is frequently wanting.

=Conjunc´tion=. The meeting of two heavenly bodies in the same point or place in the heavens.

=Constella´tion=. A number of stars which appear as if situated near each other in the heavens, and are considered as forming a particular division.

=Cynosure= (_sin´o-shōōr_ or _sī´_). A name of the constellation Ursa Minor, or the Lesser Bear, which contains, in the tail, the pole star by which mariners are guided.

=Declination= (_dek-lin-a´shun_). Distance of any object from the celestial equator, either northward or southward.

=Disk=. The face or visible projection of a celestial body, usually predicated of the sun, moon, or planets; but the stars have also apparent disks.

=Eclipse´=. An obscuration or interception of the light of the sun, moon, or other luminous body.

=Eclip´tic=. The great circle of the heavens which the sun appears to describe in his annual revolution.

=Equa´tor=. The great circle of the sphere, equally distant from the two poles of the world, or having the same poles as the world.

=Equinox= (_ē´kwi-noks_). The precise time when the sun enters one of the equinoctial points, making the day and night of equal length.

=Faculae= (_fa´ku-lē_). Certain spots sometimes seen on the sun’s disk, which appear brighter than the rest of his surface.

=Fixed Stars=. Those which retain the same or very nearly the same position with respect to each other.

=Gal´axy=. The Milky-Way.

=Gemini= (_jem´i-nī_). The third sign or constellation in the zodiac, which the sun enters about the 21st of May.

=Geocentric= (_jē-o-sen´trik_) =Par´allax=. The apparent change of a body’s place that would arise from a change of the spectator’s station from the surface to the center of the earth.

=Ha´lo=. A luminous circle, usually prismatically colored round the sun or moon, and supposed to be caused by the refraction of light through crystals of ice in the atmosphere.

=Heliocentric= (_hē-li-o-sen´trik_) =Par´allax=. The arc of the great circle of the celestial sphere, drawn from the heliocentric to the geocentric place of a body.

=Heliometer= (_hē-li-om´e-ter_). An instrument for measuring with exactness the apparent diameter of the sun, moon, planets, etc.

=Hori´zon=. A circle touching the earth at the place of the spectator, and bounded by the line in which the earth and skies seem to meet.

=Le´o= (Lat., the Lion). The fifth sign of the zodiac which the sun enters about the 22d of July.

=Libra= (_lī´bra_), the Balance. The seventh sign of the zodiac, which the sun enters at the autumnal equinox, in September.

=Luna´tion=. The period of a revolution of the moon round the earth, or the time from one new moon to the next.

=Maculae= (_mak´u-lē_). Dark spots on the surfaces of sun and moon, and on some of the planets.

=Moon=. A secondary planet or satellite of the earth, whose light, borrowed from the sun, serves to dispel the darkness of night.

=Nadir= (_nā´dir_). The point of the heavens or lower hemisphere directly opposite the zenith.

=Neb´ulae= (_neb´u-lē_). Misty appearances among the stars, usually, but not always, resolved by telescope into myriads of small stars.

=Nodes= (_nōdes_). The two points in which the orbit of a planet intersects the ecliptic.

=Nuta´tion=. A vibratory motion of the earth’s axis, arising from periodical fluctuations in the obliquity of the ecliptic.

=Occulta´tion=. The hiding of a heavenly body from our sight by the intervention of some other of the heavenly bodies.

=Or´bit=. The path described by a heavenly body in its periodical revolution.

=Par´allax=. The change of place in a heavenly body in consequence of being viewed from different points.

=Penum´bra=. A partial shadow or obscurity on the margin of the perfect shadow in an eclipse, or between the perfect shadow, where the light is entirely intercepted, and the full light.

=Perigee= (_per´i-jē_). That point in the orbit of the sun or moon in which it is at the least distance from the earth.

=Perihelion= (_per-i-hē´li-on_). That part of the orbit of a planet or comet in which it is at its least distance from the sun.

=Plan´et=. The name given to a few bright and conspicuous stars which are constantly changing their apparent situations in the celestial sphere.

=Precession= (_pre-sesh´un_) =of the Equinoxes=. A continual shifting of the equinoctial points from east to west.

=Radius Vector=. An imaginary line joining the center of the sun and the center of a body revolving about it.

=Retrocession= (_rē-tro-sesh´un_) =of the Equinoxes=. The going backward of the equinoctial points.

=Sagittarius= (_saj-i-tā´ri-us_). One of the twelve signs of the zodiac, which the sun enters about November 22.

=Sat´ellite=. A small planet revolving round another planet.

=Scor´pio=. The eighth sign of the zodiac, which the sun enters about October 23.

=Selenography= (_sel-en-og´raf-i_). The description of the surface of the moon.

=Sign=. The twelfth part of the ecliptic.

=Solstice= (_sol´stis_). The time when the sun, in its annual revolution, arrives at that point in the ecliptic farthest north or south of the equator, or reaches its greatest northern or southern declination.

=Star=. An apparently small, luminous body in the heavens, that shines in the night, or when its light is not obscured by clouds or lost in the brighter effulgence of the sun.

=Sun=. The central body of our system, about which all the planets and comets revolve, and by which their motions are regulated and controlled.

=Taurus= (_taw´rus_). The second sign of the zodiac, which the sun enters about the 20th of April.

=Virgo= (_ver´go_). The sixth sign of the zodiac, which the sun enters in August.

=Ze´nith=. The point in the heavens directly overhead.

BOOK OF THE EARTH

THE EARTH AS A PLANET

ITS STRUCTURE: INTERIOR, CRUST, ROCKS, FOSSILS, HEAT

GEOLOGICAL VIEW OF GROWTH OF THE EARTH

SURFACE OF THE EARTH: LAND FORMS: CONTINENTS, ISLANDS,
MOUNTAINS, PLAINS; WATER FORMS: SPRINGS, RIVERS, LAKES,
OCEANS

CELEBRATED MOUNTAIN PEAKS AND RANGES

ATMOSPHERE, CLIMATE AND WEATHER

NATURAL WONDERS AND FORCES: VOLCANOES, EARTHQUAKES,
GEYSERS, CAVERNS, WATERFALLS, WHIRLPOOLS, TIDES, DESERTS,
OCEAN DEPTHS, CLOUDS, SEASONS, GLACIERS, ICEBERGS, SNOW,
RAIN, HAIL, DEW, CORAL ISLANDS AND REEFS

DICTIONARY OF MINERAL PRODUCTS

TABLES FOR THE IDENTIFICATION OF MINERALS

GEMS AND PRECIOUS STONES

PRONOUNCING DICTIONARY OF SCIENTIFIC TERMS
ABOUT THE EARTH

NUMEROUS ILLUSTRATIONS, CHARTS AND MAPS

BOOK OF THE EARTH

Science tells us that the Earth was once a shining star, a globe of
liquid fire. As it cooled down, a crust formed over its surface,
composed chiefly of rocks and metals. This crust was rent by the
force of the gases shut up within, and thus the mountains, valleys,
gorges, and volcanoes were formed. The Earth, indeed, is still
upheaving and subsiding, but so slowly that we rarely feel it.
Through these agencies the distribution of land and water on the
surface of the earth has undergone great changes. The shape of the
Earth is that of a sphere somewhat flattened at the poles, and it
has a diameter of about 8,000 miles. The solid crust is called the
_lithosphere_--which is surrounded by an envelope of air--the
_atmosphere_--and in part by an envelope of water--the
_hydrosphere_.

Beneath the rocky crust of the earth, thirty-five miles in thickness, there is a broad belt of heavier material to a depth of nine hundred miles. Within this shell lies the great metallic core.]

OUR EARTH: ITS STRUCTURE AND SURFACE

Our first glimpse of the earth as a planet shows it as a nebulous star, still intensely hot, and with no solid nucleus, rotating on its own axis, and at the same time revolving around the sun in a nearly circular orbit.

WHAT THE HEAT OF THE EARTH SHOWS

At first it seems hardly possible that the earth could have been a star. But, if we go down beneath the surface of the earth, we find that at a depth of forty or fifty feet there is very slight variation in temperature. When we go yet deeper, as in mines, we find that the earth grows hotter as we descend. The temperature increases on an average about one degree Fahrenheit for every sixty-four feet descent. But this amount is variable according to the locality, geological formation, and dip of strata. In the Calumet and Hecla Mine, observations show an increase of one degree in about every one hundred and twenty-five feet. At Paris, the water from a depth of 1794 feet has a temperature of eighty-two degrees; at Salzwerth, in Germany, from a depth of 2144 feet, a temperature of ninety-one degrees. Natural hot springs, rising from unknown depths, are sometimes scalding hot. One in Arkansas has a temperature of one hundred and eighty degrees.

At a depth of twenty miles, with this continual increase of temperature, the ground must be fully red-hot; and not very much farther down the heat must be sufficient to melt every known substance. The solid earth, then, is merely a thin crust, covering a sea of liquid fire below. The streams of lava poured forth from volcanoes are a proof of the existence of this molten mass beneath our feet.

WHAT CAUSES THE INTERNAL HEAT OF THE EARTH

If we examine the solid crust of the earth we shall not long be at a loss in regard to the origin of this internal heat. We are all familiar with the burning of coal. Now coal is mainly a substance called _carbon_, and when it burns it unites with _oxygen_, one of the gases in the air. Many rarer substances, such as silicon, and the metals magnesium, calcium, and sodium, are even more inflammable than carbon, and in burning give rise to solid products. Now the rocks in the earth are found to be made up almost wholly of these very inflammable substances combined with oxygen. The solid portions of the earth, then, are nothing but the ashes and cinders of a great conflagration. Even the waters are made up of hydrogen, one of the most inflammable substances, united with this same oxygen, and, strange as it may seem, they too, are the products of combustion. When, therefore, the materials of which the earth is formed were burning, our planet must have been a fiery star, and the great heat must have reduced all the products of the conflagration to a liquid state.

HOW THE EARTH’S CRUST WAS FORMED

When the fire went out for lack of fuel the mass began to cool at the surface, and a solid crust was finally formed, which with the lapse of time became thicker and thicker. This crust shut in the steam and gases generated in the fiery ocean underneath; and these, acting upon the crust with enormous pressure, heaved it into ridges. At times the strain caused the crust to crack, and forced the melted mass up through it, and in this way hills and mountains were formed. The thicker the crust the greater the strain it would bear before it gave way, and the greater the amount of molten matter driven out through the rent. The highest mountains, then, are the last that were uplifted. In some cases the openings thus made in the crust were never completely closed, and thus volcanoes were formed. These act like safety-valves, and prevent the forces within from accumulating sufficiently to cause fresh rents. But notwithstanding the relief thus given to the pent-up forces, they still manifest themselves in earthquakes.

SHAPE OF THE EARTH A SPHEROID

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The Circle of Knowledge: A Classified, Simplified, Visualized Book of AnswersChapter II: English and American Literature -- Outline Charts of English and (2)

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