Читать книгу Everyday Objects; Or, Picturesque Aspects of Natural History - W. H. Davenport Adams - Страница 7

"Beneath the sky's triumphal arch

This music sounded like a march,

And with its chorus seemed to be

Preluding some great tragedy.

Sirius was rising in the east;

And, slow ascending one by one,

The kindling constellations shone.

Begirt with many a blazing star,

Stood the great giant Algebar,

Orion, hunter of the beast!

His sword hung gleaming by his side;

And, on his arm, the lion's hide

Scattered across the midnight air

The golden radiance of its hair."

The most ancient observer who wished, with his own eyes, to assure himself whether the number of the stars was infinite, must have quickly perceived that, in spite of an apparent impossibility, it is no difficult task to complete their enumeration. To execute this operation conveniently, however, we must invent a process; and of all processes, the simplest, and that which first occurs to the mind, is to group the stars by configurations which, to a certain degree, are mnemo-technical. Such, in our belief, is the true origin—a point so often and laboriously discussed—of the asterisms or constellations. Their fanciful, mythological, or poetical embellishments, are of later date.

The census or enumeration of the stars, which we suppose to have commenced during our winter nights, must at first have been limited to the most characteristic groups, composed of the most brilliant points. In this scientific labour the first rank would necessarily be occupied by Arctos (or Ursa Major) and Orion. Why? Because these two constellations attract and rivet everybody's gaze.

Fig. 3.—Orion.

Orion is situated on the side opposite to the Great Bear. It is the most beautiful constellation in our western sky. You may easily recognise it by three stars, very close together, which are inscribed, as it were, in the centre of a great trapezium of four stars, two of which are of the first magnitude. Beneath the three first stars, called the Three Kings, or Orion's Belt, is visible a small stellar group of the fourth and fifth magnitude, near which, with a good average glass, may be distinguished the largest and most remarkable of the nebulæ.

Here we find the mythologists—those theologians of the Greco-Roman polytheism—at disagreement. According to an ancient legend, immortalised by Homer—

"Aurora sought Orion's love,...

Till, in Ortygia, Dian's wingèd dart

Had pierced the hapless hunter to the heart."[3]

The giant, in the lower world, is still animated by a burning passion for the chase—

"There huge Orion, of portentous size,

Swift through the gloom a giant-hunter flies;

A ponderous mace of brass, with direful sway,

Aloft he whirls, to crush the savage prey;

Stern beasts in trains that by his truncheon fell,

Now, grisly forms, shoot o'er the lawns of hell."[4]

According to later traditions, the giant Orion, son of Tura and Neptune, was endowed by his father with the faculty of walking upon the sea as well as upon earth. He abandoned himself to the fierce joys of the chase in the wooded isle of Crete, to whose shades he had accompanied Diana and Latona. Swollen with pride, he defied to combat all the monsters of the universe, and was slain by a scorpion which the earth had engendered under his feet. But, through the intercession of Diana, a place was given to him in the firmament opposite Scorpio.

Diurnal Movement.

Let us put aside these dreams of the world's youth, and return to the reality.

Nature, transformed by the ancients into a multiple divinity, never fails to overwhelm with surprise the observer who interrogates her with simplicity and without any preconcerted system. And it was thus that he who first undertook to enumerate the stars, by the help of the constellations, made at once the greatest and most unexpected discovery. What, in fact, was not his astonishment on seeing the gradual displacement of objects which, at the first glance, appeared immovable!

To this very natural astonishment soon succeeded, we doubt not, a desire to analyse the phenomenon. The most beautiful constellations of the firmament, Ursa and Orion, will have their points of repery on the star-gemmed sphere. An attentive study, eagerly pursued through a certain lapse of time, would teach him that Orion rises and sets like the sun and the moon, while the Bear, remaining perpetually above the horizon, neither rises nor sets. Stimulated by curiosity, the observer would afterwards assure himself that the whole of the celestial vault revolved upon an axis, while the stars divided into groups; remain fixed, fixed in this sense, that they constantly maintain among themselves the same relations of distance. The idea of a solid sphere, to which the stars were attached like golden nails, then came quite naturally to the human mind. Such, undoubtedly, was the origin of the discovery of diurnal movement; of that general movement which carries all the stars from west to east, to bring them back to the same points in the course of one complete day.

To hear our professors of astronomy invariably repeating, that "the spectator of the starry vault may see, every moment, new stars rising above the horizon,—may see them mount the sky,—halt in their upward march when they have attained a certain elevation,—afterwards re-descend, and pass below the horizon;"—to hear, we say, these words incessantly reproduced, one would think that a cursory glance at the sky would suffice to reveal the general movement, and that what is within the ken of the first comer, should not be called a discovery.

But we see in this another of those illusions which blind contemporaries as to the time-long efforts of their predecessors to discover the very results which long ago became our common patrimony. Unquestionably, if you have eyes, you cannot fail to see the apparent movement of the earth and moon; but from thence to the relation of the whole celestial sphere is a wide interval. How many men are there who possess, on the one hand, sufficient patience to fix their gaze only for a couple of hours on the same point of the starry firmament; and, on the other, sufficient intelligence to estimate the relation of this point to a fixed point of the horizon, and to measure, by the thought, the interval separating these two points? Let each one ask himself.

Determination of the Cardinal Points.

However it may be, the discovery of the rotation of the celestial system must have been rapidly brought to perfection as it was transmitted from one generation to another. It must soon have been recognised that this sphere is inclined in such a manner that one of its poles—the poles of the world, which, in reality, are simply the prolonged extremities of the axis of terrestrial rotation—is always above the horizon, while the other remains below. And this phenomenon would lead to the geometrical conception of an axis of rotation of the celestial sphere. Thus we may explain, with perfect ease, why the Bear and the neighbouring constellations should describe perfect circles, and the other and more distant constellations only arcs of circles, of a greater or lesser diameter; finally, without even looking at the sky, we can understand that some stars there are which show themselves on the horizon, only to disappear immediately, and others which remain completely invisible to the inhabitants of our climates. By a singularly fortunate coincidence, the pole, that geometrical point around which revolve those circumpolar constellations that are continually above our horizon, is occupied by a star "well known to fame," and hence, on the faith of its renown, supposed by many people to be a star of peculiar brilliancy.[5] It is named the Polar Star (α in Ursa Minor), and is between the second and third magnitude.

Now if, with arms extended, we so place ourselves that our back shall be turned to Polaris, we shall have opposite to us the point of the arc occupied by the sun at noon; on our left the east, and on our right the west. It is thus we may easily learn our position in the absence of the orb of day.

The discovery of this simple mode of guidance was, nevertheless, an epoch in history. From thence the mariner grew bold enough to quit the coast, which he had hitherto hugged with timorous prudence, and venture out into the open sea. Thenceforth, the darkness disappeared; new countries were revealed to one another, and nations, which from time immemorial had remained apart, were brought into frequent communication.

It was with eyes fixed upon the Bear, which alone does not bathe itself in the waters of Ocean, that Ulysses set out from Calypso's enchanted island.

According to Homer, who reflects in his immortal work the condition of scientific knowledge among his contemporaries, the ocean was a great broad river, surrounding the earth with circumfluent volume, and in its waves the stars were bathed or extinguished in the evening, to be rekindled in the morning on the opposite side.

By saying that the Bear alone does not bathe in the waters of Ocean[6]—

Οῖη δʹ ἄμμορός ἐστι λοετρῶν ᾿Ωκεανοῑο—

the poet plainly shows that Ursa Minor, and the other circumpolar constellations, were unknown in his time.

If the knowledge of these constellations was from the beginning so useful and so necessary to navigation, the constellation nearest to the pole could not, at first, have served as a guide to any but a people essentially maritime. And here we find the Phœnicians, or Tyrians, in the foremost rank.

After reminding us that Ursa Major was also called Helice, or "the spiral," as in the famous passage in the "Argonauta" of Apollonius Rhodius,—

"Night in the east poured darkness; on the sea

The wakeful sailor to Orion's star

And Helicè turned heedful,"—

and Ursa Minor, Cynosura,—that is, the dog's tail,—Manilius,[7] a Latin poet, who wrote at the beginning of the Christian era, goes on to say:—

"At one of the extremities of the world's axis are two constellations, well known to the hapless mariner: they are his guides when the bait of gain impels him across the ocean. Helice is the larger, and describes the larger circle: it is recognised by its seven stars, which rival one another in splendour; and by this it is that the Greeks steer their barks. The smaller, Cynosura, describes a lesser circle: it is inferior both in size and lustre; but, according to the witness of the Tyrians, is of greater importance. For the Phœnicians no safer guide exists when they seek to approach a coast invisible from the high seas."

The testimony of Manilius is confirmed by that of Aratus and Strabo. The pseudo-Eratosthenes, in his book on the constellations, refers to Ursa Minor under the name of Φοινίκη, the "Phœnician." It appears, then, to be established that the Phœnicians were the first to group a constellation of the same general outline as Helice, the Little Bear, or Ursa Minor. But that, as we have already explained, the two constellations do not lie in the same direction, every one may see:

"Nec paribus positæ sunt frontibus; utraque caudam

Vergit in alterius rostrum, sequiturque sequentem."[8]

Not in the same direction do they face:

The one its tail towards the other's snout

Turns, and they thus, pursuing, each pursue.

Certain it is that the Phœnicians, as experienced seamen, would guide their course by the constellation lying nearest to the pole. But was this constellation the same which we now-a-days call Ursa Minor? It is quite allowable for us to put such a question, because everybody knows that, owing to the movement of the terrestrial axis around the poles of the ecliptic, the axis of the world (the terrestrial axis prolonged) is displaced to an extent which becomes perfectly appreciable at the end of a certain time.[9] We may calculate, therefore, that the pole, now situated, as we have already said, near the star Polaris (α in Ursa Minor), was formerly at some distance from it. So, at the epoch of the greatest prosperity of the Phœnician people, or about three thousand years ago, the north pole would nearly correspond with a star in Draco, now 24° 52' distant.

[This constellation is shown in fig. 2, between Ursa Major and Ursa Minor; the α in Draco is a star surrounded by a circle, like the Polar Star, α in Ursa Minor.]

That the constellation of Draco was well known to the ancients, we may gather from a passage in the "Phenomena" of Aratus, a work partly translated by Cicero:—

"The Dragon, like the sinuous course of a river, uncoils his long scaly body, and surrounds with undulating folds the two constellations of Ursa Major and Ursa Minor."

Bringing together these different facts for the sake of comparison, we arrive at the conclusion that the Polar Star, by whose scintillating light the early mariners steered their tiny keels, was not the Polaris of to-day—α in Ursa Minor—but α in the constellation of the Dragon.

The Arabs, those navigators of the Waterless Sea (as they poetically designate the desert of Sahara), have bestowed particular appellations on several stars; but they guide themselves rather by their radiance than by their position. Thus, such stars as α Draco, α Cepheus, α Cygnus, which have occupied, and, in the course of centuries, will again occupy the place of Polaris, have received no special denomination; while the stars of Ursa Major, α and β (occupying the posterior angles of the chariot), are called Dubke and Merak;[10] γ, δ, ε, ζ, η, which follow in due succession—Phegæa, or Phad, Megrez, Alioth, Mizar, and Ackaïr, or Benetnasch. Certain stars in the same constellation, which are barely visible, have also received distinctive names: such is Alcor, a star between the fifth and sixth magnitude, in the tail of Ursa Major, between Mizar and Benetnasch. This star, it is true, had a special use: it served the Arabs as the test of a good eyesight.

A further proof that the Arabs founded their stellar nomenclature almost exclusively upon the lustre and colour of the stars, is obvious in the names which they gave to the stars forming the constellation of Orion. (See Fig. 2.) Thus, α and β, two stars of the first magnitude, occupying the right or eastern shoulder, and the left or western foot of the giant-hunter, are called respectively, Betelguese and Rigel; the star γ, named Bellatrix, in the left shoulder, is of the second magnitude, like the stars δ, ε, ζ, which represent Orion's Belt, and bear the names of "the Three Kings" and "St James's Staff." Now the star η marking the right knee or inferior eastern angle of the brilliant trapezium, is only of the third magnitude; therefore, it has received no special designation.

The colour by which some stars are distinguished could not have failed to be remarked by those observers who first began to enumerate, or take census of, the celestial bodies. Thus Sirius, the most refulgent of the stars of heaven, situated in Canis Major, is of a bluish-white, like Rigel; and Arcturus, situated on the prolongation of the tail of Ursa Major, is reddish-yellow, like Betelguese.

Sirius, or the Dog-star, rose heliacally at the hottest time of the year, and hence the Greeks were accustomed to ascribe all the diseases of the season to its influence. It was—

"The star

Autumnal; of all stars, in dead of night,

Conspicuous most, and named Orion's dog:

Brightest it shines, but ominous, and dire

Disease portends to miserable man."

To sum up: the figurative grouping of the stars, the variety of their luminous magnificence, their position towards Polaris, the determination of that position by the longitudinal circles passing through the axis of the world, and twisted perpendicularly to this axis by the circles parallel to the Equator,—such is the aggregate of the elements which must, at a very early period, have presided over the enumeration of those sparkling points, each of which is the centre of a system.

Finally, are there any stars which the eye cannot perceive? Such a question would never have been propounded to the ancients. And why? Because no reasoning would have drawn from them an admission that it was possible by artificial means to enlarge the range of our eyesight. They would have deemed it madness to pretend to improve and develope what is not of human creation; the visual apparatus, as it is bestowed on us by nature, they supposed to be the most perfect instrument which man could imagine. And, in truth, nothing could fairly be objected to this way of looking at things.

The 48 constellations (21 northern, 12 zodiacal, and 15 austral) indicated by Ptolemæus, contain a total of 1026 stars, whose relative positions had been determined by Hipparchus. To undertake an enumeration of the stars, and to transmit the result to posterity, appeared to Pliny an audacity before which even a god would have recoiled (Hipparchus—ausus, rem etiam Deo improbam, annumerare posteris stellas).[11]

Yet numerous doubts had already risen in the mind of Hipparchus as to the accuracy of the number recognised. In the first place, the ancients undoubtedly knew, as we do, that the visual faculty is not the same in all individuals; that there are some who, in the same celestial space, see more stars than others. Many persons can discern up to stars of the seventh magnitude, while with others the sight fails far within that limit. The ancients must also have known, as we do, that, for the enumeration to be complete, the sky must be observed from all the points of the terrestrial surface on which man is planted. Even in our own days the catalogues of the southern heavens are far from being perfect. Finally, more than two thousand years before the time of Galileo, Democritus had already enunciated the opinion that the Milky Way was a mass of innumerable stars. All these signs should have been accepted as warnings against premature affirmations.

The invention of telescopes suddenly enlarged the question, and it became necessary to establish a line of demarcation between the number of stars visible to the naked eye and the number visible through the agency of the telescope. Argelander, the author of the "Uranometria," has found that the stars visible to the naked eye, over the entire surface of the heavens, range from 5000 to 5800. Otto Struve, employing Herschel's method of computation, has estimated at upwards of twenty millions (20,374,034) the number of stars visible with the Herschel 20-feet telescope.

But, in presence of all the nebulæ resolvable into stellar masses, and before the development of the artificial range of our sight,—in presence, finally, of that hopeless perspective which the more we discover the more we perceive how much there remains to discover,—are we not forcibly carried back to our point of departure?

Fig. 4.

Ought not the imagination which, at the first glance, led us to believe the number of stars to be infinite,—ought it not to draw us nearer to the truth?

How should the imagination reveal to us, without difficulty, what the intellect, assisted by the senses, can only discover after ages of assiduous exertion?

These questions, it seems to us, are worthy of our studious consideration.

We subjoin a table of the constellations in both hemispheres, with the number of stars in each, for the convenience of our younger readers.

Northern Constellations.
Ursa Minor, the Lesser Bear,	24
Ursa Major, the Great Bear,	87
Perseus, and Head of Medusa,	59
Auriga, the Charioteer,	66
Boötes, the Herdsman,	54
Draco, the Dragon,	80
Cepheus,	35
Canes Venatici, the Greyhounds Asteria and Chara,	28
Cor Caroli (Heart of Charles II.),	3
Triangulum, the Triangle,	16
Triangulum Minus, the Lesser Triangle,	10
Musca, the Fly,	6
Lynx,	44
Leo Minor, the Lesser Lion,	53
Coma Berenicis, Hair of Queen Berenice,	43
Cameleopardalis, the Giraffe,	58
Mons Menelaus, Mt. Menelaus,	4
Corona Borealis, the Northern Crown,	21
Serpens, the Serpent,	64
Scutum Sobieski, Sobieski's Shield,	8
Hercules, with the Dog Cerberus,	113
Serpentarius, or Ophiuchus, the Serpent-Bearer,	74
Taurus Poniatowski, Poniatowski's Bull,	7
Lyra, the Harp,	22
Vulpeculus et Anser, the Fox and Goose,	37
Sagitta, the Arrow,	18
Aquila, the Eagle, with Antinous,	71
Delphinus, the Dolphin,	18
Cygnus, the Swan,	81
Cassiopeia, the Lady in her Chair,	55
Equulus, the Horse's Head,	10
Lacerta, the Lizard,	16
Pegasus, the Flying Horse,	89
Andromeda,	11
Tarandus, the Rein-deer,	12
Southern Constellations.
Phœnix,	13
Apparatus Sculptoris, the Sculptor's Tools,	12
Eridanus Fluvius, the River Po,	84
Hydrus, the Water-Snake,	10
Cetus, the Whale,	97
Fornax Chemica, the Chemical Furnace,	19
Horologium, the Clock,	12
Rheticulus Rhomboidialus,	10
Xiphias Dorado, the Sword-Fish,	7
Celapraxitellis, the Engraver's Tools,	16
Lepus, the Hare,	19
Columba Noachi, Noah's Dove,	10
Orion,	78
Argo Navis, the Ship Argo,	64
Canis Major, the Great Dog,	31
Equulus Pictoris,	8
Monoceros, the Unicorn,	31
Canis Minor, the Lesser Dog,	14
Chameleon,	10
Pyxis Nautica, the Mariner's Compass,	4
Piscis Volans, the Flying-Fish,	8
Hydra, the Serpent,	60
Sextans, the Sextant,	41
Robur Carolinum (Charles II.'s Oak),	12
Antlia Pneumatica, the Air-Pump,	3
Crater, the Cup,	31
Corvus, the Crow,	9
Crux, the Cross,	6
Apis Musca, the Bee or Fly,	4
Avis Indica, the Bird of Paradise,	11
Circinus, the Mariner's Compass,	4
Centaurus, the Centaur,	35
Lupus, the Wolf,	24
Norma, or Euclid's Square,	12
Triangulum Australe, the Southern Triangle,	5
Ara, the Altar,	9
Telescopium, the Telescope,	9
Corona Australis, the Southern Crown,	12
Pavo, the Peacock,	14
Indus, the Indian,	12
Microscopium, the Microscope,	10
Octans Hadliensis, Hadley's Octant,	43
Grus, the Crane,	14
Toucan, the American Goose,	9
Piscis Australis, the Southern Fish,	24
Mons Mensa, the Table Mountain,	30
Zodiacal Constellations.
Aries, the Ram,	66
Taurus, the Bull,	141
Gemini, the Twins,	85
Cancer, the Crab,	83
Leo, the Lion,	95
Virgo, the Virgin,	110
Libra, the Balance,	51
Scorpio, the Scorpion,	44
Sagittarius, the Archer,	69
Capricornus, the Goat,	51
Aquarius, the Water-Bearer,	108
Pisces, the Fishes,	113