Plate V.Plate V.—The Legends of the Druids.
The first of November was with the Druids a night full of mystery, in which they annually celebrated the reconstruction of the world. A terrible rite was connected with this; for the Druidess nuns were obliged at this time to pull down and rebuild each year the roof of their temple, as a symbol of the destruction and renovation of the world. If one of them, in bringing the materials for the new roof, let fall her sacred burden, she was lost. Her companions, seized with a fanatic transport, rushed upon her and tore her to pieces, and scarcely a year is said to have passed without there being one or more victims. On this same night the Druids extinguished the sacred fire, which was kept continually burning in the sacred precincts, and at that signal all the fires in the island were one by one put out, and a primitive night reigned throughout the land. Then passed along to the west the phantoms of those who had died during the preceding year, and were carried away by boats to the judgment-seat of the god of the dead. (Plate V.) Although Druidism is now extinct, the relics of it remain to this day, for in our calendar we still find November 1 marked as All Saints' Day, and in the pre-Reformation calendars the last day of October was marked All Hallow Eve, and the 2nd of November as All Souls'; indicating clearly a three days' festival of the dead, commencing in the evening, and originally regulated by the Pleiades—an emphatic testimony how much astronomy has been mixed up with the rites and customs even of the English ofto-day. In former days the relics were more numerous, in the Hallowe'en torches of the Irish, the bonfires of the Scotch, thecoel-coethfires of the Welsh, and thetindlefires of Cornwall, all lighted on Hallowe'en. In France it still lingers more than here, for to this very day the Parisians at this festival repair to the cemeteries, and lunch at the graves of their ancestors.
If the extreme antiquity of a rite can be gathered from the remoteness of the races that still perform it, the fact related to us by Prescott in hisHistory of the Conquest of Mexicocannot fail to have great interest. There we find that the great festival of the Mexican cycle was held in November, at the time of the midnight culmination of the Pleiades. It began at sunset, and at midnight as that constellation approached the zenith, a human victim, was offered up, to avert the dread calamity which they believed impended over the human race. They had a tradition that the world had been previously destroyed at this time, and they were filled with gloom and dismay, and were not at rest until the Pleiades were seen to culminate, and a new cycle had begun; this great cycle, however, was only accomplished in fifty-two years.
It is possible that the festival of lanthorns among the Japanese, which is celebrated about November, may be also connected with this same day, as it is certain that that nation does reckon days by the Pleiades.
These instances of a similar festival at approximately thesame period of the year, and regulated (until fixed to a particular day in a solar calendar) by the midnight culmination of the Pleiades, show conclusively how great an influence that constellation has had on the manners and customs of the world, and throw some light on the history of man.
Even where we find no festival connected with the particular position of the Pleiades which is the basis of the above, they still are used for the regulation of the seasons—as amongst the Dyaks of Borneo. This race of men are guided in their farming operations by this constellation. "When it is low in the east at early morning, before sunrise, the elders know it is time to cut down the jungle; when it approaches mid-heaven, then it is time to burn what they have cut down; when it is declining towards the west, then they plant; and when in the early evening it is seen thus declining, then they may reap in safety and in peace;" the latter period is also that of their feast ofNycapian, or first-fruits.
We find the same regulations amongst the ancient Greeks in the days of Hesiod, who tells us that the corn is to be cut when the Pleiades rise, and ploughing is to be done when they set. Also that they are invisible for forty days, and reappear again at harvest. When the Pleiades rise, the care of the vine must cease; and when, fleeing from Orion, they are lost in the waves, sailing commences to be dangerous. The name, indeed, by which we now know these stars is supposed to be derived from the word πλεῖν, to sail—because sailing was safe afterthey had risen; though others derive it from Ï€Îλειαι, a flight of doves.
Any year that is regulated by the Pleiades, or by any other group of stars, must, as we have seen before, be what is called a sidereal, and not a solar year. Now a year in uncivilised countries can only mean a succession of seasons, as is illustrated by the use of the expression "a person of so many summers." It is difficult of course to say when any particular season begins by noticing its characteristics as to weather; even the most regular phenomena are not certain enough for that; we cannot say that when the days and nights become exactly equal any marked change takes place in the temperature or humidity of the atmosphere, or in any other easily-noticed phenomena. The day therefore on which spring commences is arbitrary, except that, inasmuch as spring depends on the position of the sun, its commencement, ought to be regulated by that luminary, and not by some star-group which has no influence in the matter. Nevertheless the position of such a group is much more easily observed, and in early ages could almost alone be observed; and so long as the midnight culmination of the Pleiades—judged of, it must be noticed, by their appearanceon the horizonat sunset—fairly coincided with that state of weather which might be reckoned the commencement of spring conditions, no error would be detected, because the change in their position is so slow. The solar spring is probably a later discovery,which now, from its greater reasonableness and constancy, has superseded the old one. But since the time of the sun's crossing the equator is the natural commencement of spring, whether discovered or not, it is plain that no group of stars could be taken as a guide instead, if their indication did not approximately coincide with this.
If then we can determine the exact date at which the Pleiades indicated by their midnight culmination the sun's passage across the equator, we can be sure that the spring could only have been regulated by this during, say, a thousand years at most, on either side of this date. It is very certain that if the method of reckoning spring by the stars had been invented at a more remote date, some other set of stars would have been chosen instead.
Now when was this date? It is a matter admitting of certain calculation, depending only on numbers derived from observation in our own days and records of the past few centuries, and the answer is that this date is about 2170B.C.
We have seen that, though it was probably brought from the southern hemisphere, the Egyptians adopted the year of the Pleiades, and celebrated the new-year's festival of the dead; but they were also advanced astronomers, and would soon find out the change that took place in the seasons when regulated by the stars. And to such persons the date at which the two periods coincided, or at least were exactly half a year apart, would be one of great importance and interest, andthere seems to be evidence that they did commemorate it in a very remarkable manner. The evidence, however, is all circumstantial, and the conclusion therefore can only claim probability. The evidence is as follows:—The most remarkable buildings of Egypt are the pyramids. These are of various sizes and importance, but are built very much after the same plan. They seem, however, to be all copies from one, the largest, namely, the Pyramid of Gizeh, and to be of subsequent date to this. Their object has long been a puzzle, and the best conclusion has been supposed to be that they were for sepulchral purposes, as in some of them coffins have been found. The large one, however, shows far more than the rest of the structure, and cannot have been meant for a funeral pile alone.
Its peculiarities come out on a careful examination and measurement such as it has been subjected to at the devoted hands of Piazzi Smyth, the Astronomer Royal for Scotland. He has shown that it is not built at random, as a tomb might be, but it is adjusted with exquisite design, and with surprising accuracy. In the first place it lies due north, south, east, and west, and the careful ascertainment of the meridian of the place, by modern astronomical instruments, could not suggest any improvement in its position in this respect. The outside of it is now, so to speak, pealed, that is to say, there was originally, covering the whole, another layer of stones which have been taken away. These stones, which were of a different material, were beautifully polished, as some of the remaining ones, now covered and concealed, can testify. The angle at which they are cut, and which of course gives the angle and elevation of the whole pyramid, is such that the height of it is in the same proportion to its circumference or perimeter, as the radius of a circle is to its circumference approximately. The height, in fact, is proved by measurement and observation to be 486 ft., and the four sides together to be 3,056 ft., or about 62/7times the height. It does not seem improbable that, considering their advancement, the Egyptians might have calculated approximately how much larger the circumference of the circle is than its diameter, and it is a curious coincidence that the pyramid expresses it. Professor Piazzi Smyth goes much further and believes that they knew, or were divinely taught, the shape and size of the earth, and by a little manipulation of the length of their unit, or as he expresses it the "pyramid inch," he makes the base of the pyramid express the number of miles in the diameter of the earth.
Now in the interior of the apparently solid structure, besides the usual slanting passage down to a kind of cellar or vault beneath the middle of the base, which may have been used for a sepulchral resting-place, there are two slanting passages, one running north and the other running south, and slanting up at different angles. Part of that which leads south is much enlarged, and is known as the grand gallery.It is of a very remarkable shape, being perfectly smooth and polished along its ascending base, as indeed it is in every part, and having a number of steps or projections, pointing also upwards at certain angles, very carefully maintained. Whether we understand its use or not, it is very plain that it has been made with a very particular design, and one not easily comprehended. This leads into a chamber known as the king's chamber, whose walls are exquisitely polished and which contains a coffer known asCheops' Coffin. This coffer has been villainously treated by travellers, who have chipped and damaged it, but originally it was very carefully made and polished. It is too large to have been brought in by the only entrance into the chamber after it was finished, and therefore is obviously no coffin at all, as is proved also by the elaborateness of the means of approach. Professor Piazzi Smyth has made the happy suggestion that it represents their standard of length and capacity, and points out the remarkable fact that it contains exactly as much as four quarters of our dry measure. As no one has ever suggested what our "quarters" are quarters of, Professor Smyth very naturally supplies the answer—"of the contents of the pyramid coffer." There are various other measurements that have been made by the same worker, and their meaning suggested in his interesting book,Our Inheritance in the Great Pyramid, which we may follow or agree to as we can; but from all that has been said above, it will appear probable thatthis pyramid was built with a definite design to mark various natural phenomena or artificial measures, which is all we require for our present purpose. Now we come to the question, what is the meaning of the particular angles at which the north-looking and south-looking passages rise, if, as we now believe, they must havesomemeaning.
The exits of these passages were closed, and they could not therefore have been for observation, but they may have been so arranged as to be a memorial of any remarkable phenomena to be seen in those directions. To ascertain if there be any such to which they point, we must throw back the heavens to their position in the days of the Egyptians, because, as we have seen, the precession of the equinoxes alters the meridian altitude of every star. As the passages point north and south, if they refer to any star at all, it must be to their passing the meridian.
Now let us take the heavens as they were 2170B.C., the date at which the Pleiadesreallycommenced the spring, by their midnight culmination, and ask how high they would be then. The answer of astronomy is remarkable—"Exactly at that height that they could be seen in the direction of the southward-pointing passage of the pyramid." And would any star then be in a position to be seen in the direction of the other or northward-looking passage? Yes, the largest star in the constellation of the Dragon, which would be so near the pole (3° 52´) as to be taken as the Pole Star in those days.These are such remarkable coincidences in a structure admittedly made with mathematical accuracy and design, and truly executed, that we cannot take them to be accidental, but must endeavour to account for them.
The simplest explanation seems to be, that everything in the pyramid is intended to represent some standard or measure, and that these passages have to do with their year. They had received the year of the Pleiades from a remoter antiquity than their own, they had discovered the true commencement of solar spring, as determined from the solar autumnal equinox, and they commemorated by the building of the pyramid the coincidence of the two dates, making passages in it which would have no meaning except at that particular time.
Whether the pyramid was builtat that time, or whether their astronomical knowledge was sufficient to enable them to predict it and build accordingly, just as we calculate back to it, we have no means of knowing. It is very possible that the pyramid may have been built by some immigrating race more learned in astronomy, like the Accadians among the Babylonians.
Either the whole of the conclusions respecting the pyramid is founded on pure imagination and the whole work upon it thrown away, or we have here another very remarkable proof of the influence of the Pleiades on the reckoning of the year, and a very interesting chapter in the history of the heavens.
Following the guidance of Mr. Haliburton, we shall find still more customs, and names depending in all probability on the influence the Pleiades once exerted, and the observances connected with the feasts in their honour.
The name by which the Pleiades are known among the Polynesians is the "Tau," which means a season, and they speak of the years of the Tau, that is of the Pleiades. Now we have seen that the Egyptians had similar feasts at similar times, in relation to this constellation, and argued that they did not arise independently. This seems still further proved by their name for these stars—the Atauria.
Now the Egyptians do not appear to have derived their signs of the Zodiac from the same source; these had a Babylonian origin, and the constellation in which the Pleiades were placed by the latter people was the Bull, by whatever name he went. The Egyptians, we may make the fair surmise, adopted from both sources; they took the Pleiades to indicate the Bull, and they called this animal after the Atauria. From thence we got the Latin Taurus, and the German Thier.
It is possible that this somehow got connected with the letter "tau" in Greek, which seems itself connected with the sacred scarabæus or Tau-beetle of Egypt; but the nature of the connection is by no means obvious. Mr. Haliburton even suggests that the "tors" and "Arthur's seat," which are names given to British hill-tops, may be connected with the"high places," of the worship of the Pleiades, but of this we have no proof.
Among the customs possibly derived from the ancients, through the Phœnicians, though now adopted as conveying a different meaning in a Christian sense, is that of the "hot cross bun," or "bull cake." It is found on Egyptian monuments, signifying the four quarters of the year, and sometimes stamped with the head and horns of the bull. It is found among ourselves too, essentially connected with the dead, and something similar to it appears in the "soul cake" connected originally with All Souls' Day.
Among the Scotch it was traditionally thought that on New Year's Eve the Candlemas Bull can be seen, rising at twilight and sailing over the heavens—a very near approach to a matter-of-fact statement.
We have seen that among the ancient Indians there was some notice taken of the Pleiades, and that they in all probability guided their year by them or by some other stars: it would therefore behove them to know something of the precession of the equinoxes. It seems very well proved that their days of Brahma and other periods were meant to represent some astronomical cycles, and among these we find one that is applicable to the above. They said that in every thousand divine ages, or in every day of Brahma, fourteen Menus are successively invested with the sovereignty of the earth. Each Menu transmits his empire to his sons duringseventy-one divine ages. We may find a meaning for this by putting it that the equinox goes forward fourteen days in each thousand years, and each day takes up seventy-one years.
These may not be the only ones among the various customs, sayings, and names that are due in one way or other to this primitive method of arranging the seasons by the positions of the stars, especially of those most remarkable and conspicuous ones the Pleiades, but they are those that are best authenticated. If the connection between the Pleiades and the festival of the dead, the new year and a deluge, can be clearly made out; if the tradition of the latter be found as universal as that of the former, and be connected with it in the Mosaic narrative; if we can trace all these traditions to the south of the equator, and find numerous further traditions connected with islands, we may find some reason for believing in their theory who suggest that the early progenitors of the human race (? all of them) were inhabitants of some fortunate islands of even temperature in the southern hemisphere, where they made some progress in civilisation, but that their island was swallowed up by the sea, and that they only escaped by making huge vessels, and, being carried by the waves, they landed on continental shores, where they commemorated yearly the great catastrophe that had happened to them, notifying its time by the position of the Pleiades, making it a feast of the dead whom they had leftbehind, and opening the year with the day, whether it were spring or not, and handing down to their descendants and to those among whom they came, the traditions and customs which such events had impressed upon them.
Whether such an account be probable, mythical, or unnatural, there are certainly some strange things to account for in connection with the Pleiades.
Many and various have been the ideas entertained by reflecting men in former times on the nature and construction of the heavenly vault, wherein appeared those stars and constellations whose history we have already traced. Is it solid? or liquid? or gaseous? Each of these and many other suppositions have been duly formulated by the ancient philosophers and sages, although, as we are told by modern astronomy, it does not exist at all.
In our study of the ancient ideas about the structure of the universe, we will commence with that early and curious system which considered the heavenly vault to be material and solid.
The theory of a solid sky received the assent of all the most ancient philosophers. In his commentary on Aristotle's work on the heavens, Simplicius reveals the repugnance the ancient philosophers felt in admitting that a star could stand alone in space, or have a free motion of its own. Itmust have a support, and they therefore conceived that the sky must be solid. However strange this idea may now appear, it formed for many centuries the basis of all astronomical theories. Thus Anaximenas (in the sixth centuryB.C.) is related by Plutarch to have said that "the outer sky is solid and crystalline," and that the stars are "fixed to its surface like studs," but he does not say on what this opinion was founded, though it is probable that, like his master Anaximander, he could not understand how the stars could move without being supported.
Pythagoras, who lived about the same epoch, is also supposed by some to have held the same views, and it is possible that they all borrowed these ideas from the Persians, whose earliest astronomers are said in theZend avestato have believed in concentric solid skies.
Eudoxus of Cnidus, in the fifth centuryB.C., is said by his commentator Aratus to have also believed in the solidity of the heavens, but his reasons are not assigned.
Notwithstanding these previously expressed opinions, Aristotle (fourth century,B.C.) has for a long time been generally supposed to be the inventor of solid skies, but in fact he only gave the idea his valuable and entire support. The sphere of the stars was his eighth heaven. The less elevated heavens, in which he also believed, were invented to explain as well as they might, the proper motions of the sun, moon, and planets.
The philosopher of Stagira said that the motion of his eighth or outermost solid sky was uniform, nor ever troubled by any perturbation. "Within the universe there is," he says, "a fixed and immovable centre, the earth; and without there is a bounding surface enclosing it on all sides. The outermost part of the universe is the sky. It is filled with heavenly bodies which we know as stars, and it has a perpetual motion, carrying round with it these immortal bodies in its unaltering and unending revolution."
Euclid, to whom we may assign a date of about 275 before our present era, also considered the stars to be set in a solid sphere, having the eye of the observer as centre; though for him this conception was simply a deduction from exact and fundamental observations, namely, that their revolution took place as a whole, the shape and size of the constellation being never altered.
Cicero, in the last century before Christ, declared himself a believer in the solidity of the sky. According to him the ether was too rarefied to enable it to move the stars, which must therefore require to be fixed to a sphere of their own, independent of the ether.
In the time of Seneca there seem to have been difficulties already raised about the solidity of the heavens, for he only mentions it in the form of a question—"Is the sky solid and of a firm and compact substance?" (Questions, Book ii.)
In the fifth century the idea of the star sphere still lingered, and in the eyes of Simplicius, the commentator of Aristotle, it was not merely an artifice suitable for the representation of the apparent motions, but a firm and solid reality; while Mahomet and most of the Fathers of the Christian Church had the same conception of these concentric spheres.
It appears then from this review that the phrases "starry vault," and especially "fixed stars," have been used in two very distinct senses. When we meet with them in Aristotle or Ptolemy, it is obvious that they have reference to the crystal sphere of Anaximenas, to which they were supposed to be affixed, and to move with it; but that later the word "fixed" carried with it the sense of immovable, and the stars were conceived as fixed in this sense, independently of the sphere to which they were originally thought to be attached. Thus Seneca speaks of them as thefixum et immobilem populum.
If we would inquire a little further into the supposed nature of this solid sphere, we find that Empedocles considered it to be a solid mass, formed of a portion of the ether which the elementary fire has converted into crystal, and his ideas of the connection between cold and solidification being not very precise, he described it by names that give the best idea of transparence, and, like Lactantius, called itvitreum cælum, or saidcælum ærem glaciatum esse, though we cannot suppose that he made any allusion to what we now call glass,but simply meant some body eminently transparent into which the fire had transformed the air; while so far from having any idea of cold, as we might imagine possible from observations of the snowy tops of mountains, they actually believed in a warm region above the lower atmosphere. Thus Aristotle considers that the spheres heat by their motion the air below them, without being heated themselves, and that there is thus a production of heat. "The motion of the sphere of fixed stars," he says, "is the most rapid, as it moves in a circle with all the bodies attached to it, and the spaces immediately below are strongly heated by the motion, and the heat, thus engendered, is propagated downwards to the earth." This however, strangely enough, does not appear to have prevented their supposing an eternal cold to reign in the regions next below, for Macrobius, in his commentary on Cicero, speaks of the decrease of temperature with the height, and concludes that the extreme zones of the heavens where Saturn moves must be eternally cold; but this they reckoned as part of the atmosphere, beyond whose limits alone was to be found the fiery ether.
It is to the Fathers of the Church that we owe the transmission during the middle ages of the idea of a crystal vault. They conceived a heaven of glass composed of eight or ten superposed layers, something like so many skins in an onion. This idea seems to have lingered on in certain cloisters of southern Europe even into the nineteenth century, for avenerable Prince of the Church told Humboldt in 1815, that a large aërolite lately fallen, which was covered with a vitrified crust, must be a fragment of the crystalline sky. On these various spheres, one enveloping without touching another, they supposed the several planets to be fixed, as we shall see in a subsequent chapter.
Whether the greater minds of antiquity, such as Plato, Plutarch, Eudoxus, Aristotle, Apollonius, believed in the reality of these concentric spheres to carry the planets, or whether this conception was not rather with them an imaginary one, serving only to simplify calculation and assist the mind in the solution of the difficult problem of their motion, is a point on which even Humboldt cannot decide. It is certain, however, that in the middle of the sixteenth century, when the theory involved no less than seventy-seven concentric spheres, and later, when the adversaries of Copernicus brought them all into prominence to defend the system of Ptolemy, the belief in the existence of these solid spheres, circles and epicycles, which was under the especial patronage of the Church, was very widespread.
Tycho Brahe expressly boasts of having been the first, by considerations concerning the orbits of the comets, to have demonstrated the impossibility of solid spheres, and to have upset this ingenious scaffolding. He supposed the spaces of our system to be filled with air, and that this medium,disturbed by the motion of the heavenly bodies, opposed a resistance which gave rise to the harmonic sounds.
It should be added also that the Grecian philosophers, though little fond of observation, but rejoicing rather in framing systems for the explanation of phenomena of which they possessed but the faintest glimpse, have left us some ideas about the nature of shooting stars and aërolites that come very close to those that are now accepted. "Some philosophers think," says Plutarch in his life of Lysander, "that shooting stars are not detached particles of ether which are extinguished by the atmosphere soon after being ignited, nor do they arise from the combustion of the rarefied air in the upper regions, but that they are rather heavenly bodies which fall, that is to say, which escaping in some way from the general force of rotation are precipitated in an irregular manner, sometimes on inhabited portions of the earth, but sometimes also in the ocean, where of course they cannot be found." Diogenes of Apollonius expresses himself still more clearly: "Amongst the stars that are visible move others that are invisible, to which in consequence we are unable to give any name. These latter often fall to the earth and take fire like that star-stone which fell all on fire near Ægos Potamos." These ideas were no doubt borrowed from some more ancient source, as he believed that all the stars were made of something like pumice-stone. Anaxagoras, in fact, thought that all the heavenly bodies were fragments ofrocks which the ether, by the force of its circular motion, had detached from the earth, set fire to, and turned into stars. Thus the Ionic school, with Diogenes of Apollonius, placed the aërolites and the stars in one class, and assigned to all of them a terrestrial origin, though in this sense only, that the earth, being the central body, had furnished the matter for all those that surround it.
Plutarch speaks thus of this curious combination:—"Anaxagoras teaches that the ambient ether is of an igneous nature, and by the force of its gyratory motion it tears off blocks of stone, renders them incandescent, and transforms them into stars." It appears that he explained also by an analogous effect of the circular motion the descent of the Nemæan Lion, which, according to an old tradition, fell out of the moon upon the Peloponnesus. According to Bœckh, this ancient myth of the Nemæan Lion had an astronomical origin, and was symbolically connected in chronology with the cycle of intercalation of the lunar year, with the worship of the moon in Nemaea, and the games by which it was accompanied.
Anaxagoras explains the apparent motion of the celestial sphere from east to west by the hypothesis of a general revolution, the interruption of which, as we have just seen, caused the fall of meteoric stones. This hypothesis is the point of departure of the theory of vortices, which more than two thousand years later, by the labours of Descartes,Huyghens, and Hooke, took so prominent a place among the theories of the world.
Plate VI.Plate VI.—The Nemæan Lion.
It may be worth adding with regard to the famous aërolite of Ægos Potamus, alluded to above, that when the heavens were no longer believed to be solid, the faith in the celestial origin of this, as of other aërolites, was for a long time destroyed. Thus Bailly the astronomer, alluding to it, says, "if the fact be true, this stone must have been thrown out by a volcano." Indeed it is only within the last century that it has been finally accepted for fact that stones do fall from the sky. Laplace thought it probable that they came from the moon; but it has now been demonstrated that aërolites, meteors, and shooting stars belong all to one class of heavenly bodies, that they are fragments scattered through space, and circulate like the planets round the sun. When the earth in its motion crosses this heavenly host, those which come near enough to touch its atmosphere leave a luminous train behind them by their heating by friction with the air: these are theshooting stars. Sometimes they come so close as to appear larger than the moon, then they aremeteors;and sometimes too the attraction of the earth makes them fall to it, and these becomeaërolites.
But to return to our ancient astronomers:—
They believed the heavens to be in motion, not only because they saw the motion with their eyes, but because they believed them to be animated, and regarded motion asthe essence of life. They judged of the rapidity of the stars' motion by a very ingenious means. They perceived that it was greater than that of a horse, a bird, an arrow, or even of the voice, and Cleomenas endeavoured to estimate it in the following way. He remarks that when the king of Persia made war upon Greece he placed men at certain intervals, so as to lie in hearing of each other, and thus passed on the news from Athens to Susa. Now this news took two days and nights to pass over this distance. The voice therefore only accomplished a fraction of the distance that the stars had accomplished twice in the same time.
The heavens, as we have seen, were not supposed to consist of a single sphere, but of several concentric ones, the arrangement and names of which we must now inquire into.
The early Chaldeans established three. The first was the empyreal heaven, which was the most remote. This, which they called also the solid firmament, was made of fire, but of fire of so rare and penetrating a nature, that it easily passed through the other heavens, and became universally diffused, and in this way reached the earth. The second was the ethereal heaven, containing the stars, which were simply formed of the more compact and denser parts of this substance; and the third heaven was that of the planets. The Persians, however, gave a separate heaven to the sun, and another to the moon.
The system which has enjoyed the longest and most widely-spread reign is that which places above, or rather round, the solid firmament a heaven of water—(the nature of which is not accurately defined), and round this aprimum mobile, prime mover, or originator of all the motions, and round all this the empyreal heaven, or abode of the blessed. In the most anciently printed scientific encyclopædia known, theMagarita philosophica, edited in the fifteenth century, that is, two centuries before the adoption of the true system of the world, we have the curious figure represented on the next page, in which we find no less than eleven different heavens. We here see on the exterior the solid empyreal heaven, which is stated in the body of the work to be the abode of the blessed and to be immovable, while the next heaven gives motion to all within, and is followed by the aqueous heaven, then the crystal firmament, and lastly by the several heavens of the planets, sun, and moon. The revolution of these spheres was not supposed to take place, like the motion of the earth in modern astronomy, round an imaginary axis, but round one which had a material existence, which was provided with pivots moving in fixed sockets. Thus Vitruvius, architect to Augustus, teaches it expressly in these words:—
"The heaven turns continually round the earth and sea upon an axis, where two extremities are like two pivots that sustain it: for there are two places in which the Governor of Nature has fashioned and set these pivots as two centres; one is above the earth among the northern stars; the other is atthe opposite end beneath the earth to the south; and around these pivots, as round two centres, he has placed little naves, like those of a wheel upon which the heaven turns continually."
Fig. 13.Fig. 13.
Similarly curious ideas we shall find to have prevailed with respect to the meaning of everything that they observed in the heavens: thus what a number of opinions have been hazarded on the nature of the "Milky Way" alone! some of which we may learn from Plutarch. The Milky Way, he says, is a nebulous circle, which constantly appears in the sky, and which owes its name to its white appearance. Certain Pythagoreans assert that when Phaeton lit up the universe, one star, which escaped from its proper place, set light to the whole space it passed over in its circular course, and so formed the Milky Way. Others thought that this circle was where the sun had been moving at the beginning of the world. According to others it is but an optical phenomenon produced by the reflection of the sun's rays from the vault of the sky as from a mirror, and comparable with the effects seen in the rainbow and illuminated clouds. Metrodorus says it is the mark of the sun's passage which moves along this circle. Parmenidas pretends that the milky colour arises from a mixture of dense and rare air. Anaxagoras thinks it an effect of the earth's shadow projected on this part of the heavens, when the sun is below. Democritus says that it is the lustre of several little stars which are very near together, and which reciprocally illuminate each other. Aristotle believes it to be a vast mass of arid vapours, which takes fire from a glowing tress, above the region of the ether, and far below that of the planets. Posidonius says that thecircle is a compound of fire less dense than that of the stars, but more luminous. All such opinions, except that of Democritus, are of little value, because founded on nothing; perhaps the worst is that of Theophrastus, who said it was the junction between the two hemispheres, which together formed the vault of heaven: and that it was so badly made that it let through some of the light that he supposed to exist everywhere behind the solid sky.
We now know that the Milky Way, like many of the nebulæ, is an immense agglomeration of suns. The Milky Way is itself a nebula, a mass of sidereal systems, with our own among them, since our sun is a single star in this vast archipelago of eighteen million orbs. The Greeks called it the Galaxy. The Chinese and Arabians call it the River of Heaven. It is the Path of Souls among the North American Indians, and the Road of S. Jacques de Compostelle among French peasants.
In tracing the history of ideas concerning the structure of the heavens among the Greek philosophers, we meet with other modifications which it will be interesting to recount. Thus Eudoxus, who paid greater attention than others to the variations of the motions of the planets, gave more than one sphere to each of them to represent these observed changes. Each planet, according to him, has a separate part of the heaven to itself, which is composed of several concentric spheres, whose movements, modifying each other,produce that of the planet. He gave three spheres to the sun: one which turned from east to west in twenty-four hours, to represent the diurnal rotation; a second, which turned about the pole of the ecliptic in 365¼ days, and produced its annual movement; and a third was added to account for a certain supposed motion, by which the sun was drawn out of the ecliptic, and turned about an axis, making such an angle with that of the ecliptic, as represented the supposed aberration. The moon also had three spheres to produce its motions in longitude and latitude, and its diurnal motion. Each of the other planets had four, the extra one being added to account for their stations and retrogressions. It should be added that these concentric spheres were supposed to fit each other, so that the different planets were only separated by the thicknesses of these crystal zones.
Polemarch, the disciple of Eudoxus, who went to Athens with his pupil Calippus for the express purpose of consulting Aristotle on these subjects, was not satisfied with the exactness with which these spheres represented the planetary motions, and made changes in the direction of still greater complication. Instead of the twenty-six spheres which represented Eudoxus' system, Calippus established thirty-three, and by adding also intermediary spheres to prevent the motion of one planet interfering with that of the adjacent ones, the number was increased to fifty-six.
There is extant a small work, ascribed to Aristotle, entitled "Letter of Aristotle to Alexander on the system of the world," which gives so clear an account of the ideas entertained in his epoch that we shall venture to give a somewhat long extract from it. The work, it should be said, is not by all considered genuine, but is ascribed by some to Nicolas of Damas, by others to Anaximenas of Lampsacus, a contemporary of Alexander's, and by others to the Stoic Posidonius. It is certain, however, that Aristotle paid some attention to astronomy, for he records the rare phenomena of an eclipse of Mars by the moon, and the occultation of one of the Gemini by the planet Jupiter, and the work may well be genuine. It contains the following:—
"There is a fixed and immovable centre to the universe. This is occupied by the earth, the fruitful mother, the common focus of every kind of living thing. Immediately surrounding it on all sides is the air. Above this in the highest region is the dwelling-place of the gods, which is called the heavens. The heavens and the universe being spherical and in continual motion, there must be two points on opposite sides, as in a globe which turns about an axis, and these points must be immovable, and have the sphere between them, since the universe turns about them. They are called the poles. If a line be drawn from one of these points to the other it will be the diameter of the universe, having the earth in the centre and the two poles at theextremities; of these two poles the northern one is always visible above our horizon, and is called the Arctic pole; the other, to the south, is always invisible to us—it is called the Antarctic pole.
"The substance of the heavens and of the stars is called ether; not that it is composed of flame, as pretended by some who have not considered its nature, which is very different from that of fire, but it is so called because it has an eternal circular motion, being a divine and incorruptible element, altogether different from the other four.
"Of the stars contained in the heavens some are fixed, and turn with the heavens, constantly maintaining their relative positions. In their middle portion is the circle called thezoophore, which stretches obliquely from one tropic to the other, and is divided into twelve parts, which are the twelve signs (of the zodiac). The others are wandering stars, and move neither with the same velocity as the fixed stars, nor with a uniform velocity among themselves, but all in different circles, and with velocities depending on the distances of these circles from the earth.
"Although all the fixed stars move on the same surface of the heavens, their number cannot be determined. Of the movable stars there are seven, which circulate in as many concentric circles, so arranged that the lower circle is smaller than the higher, and that the seven so placed one within the other are all within the spheres of the fixed stars.
"On the nearer, that is inner, side of this ethereal, immovable, unalterable, impassible nature is placed our movable, corruptible, and mortal nature. Of this there are several kinds, the first of which is fire, a subtle inflammable essence, which is kindled by the great pressure and rapid motion of the ether. It is in this region of air, when any disturbance takes place in it, that we see kindled shooting-stars, streaks of light, and shining motes, and it is there that comets are lighted and extinguished.
"Below the fire comes the air, by nature cold and dark, but which is warmed and enflamed, and becomes luminous by its motion. It is in the region of the air, which is passive and changeable in any manner, that the clouds condense, and rain, snow, frost, and hail are formed and fall to the earth. It is the abode of stormy winds, of whirlwinds, thunder, lightning, and many other phenomena.
"The cause of the heaven's motion is God. He is not in the centre, where the earth is a region of agitation and trouble, but he is above the outermost circumference, which is the purest of all regions, a place which we call rightlyouranos, because it is the highest part of the universe, andolympos, that is, perfectly bright, because it is altogether separated from everything like the shadow and disordered movements which occur in the lower regions."
We notice in this extract a curious etymology of the word ether, namely, as signifying perpetual motion (ἀεὶ τεεῖν),though it is more probable that its true, as its more generally accepted derivation is from αἴθειν, to burn or shine, a meaning doubtless alluded to in a remarkable passage of Hippocrates, ΠεÏὶ ΣάÏκων. "It appears to me," he says, "that what we call the principle of heat is immortal, that it knows all, sees all, hears all, perceives all, both in the past and in the future. At the time when all was in confusion, the greater part of this principle rose to the circumference of the universe; it is this that the ancients have calledether."
The first Greek that can be called an astronomer was Thales, born at Miletus 641B.C., who introduced into Greece the elements of astronomy. His opinions were these: that the stars were of the same substance as the earth, but that they were on fire; that the moon borrowed its light from the sun, and caused the eclipses of the latter, while it was itself eclipsed when it entered the earth's shadow; that the earth was round, and divisible into five zones, by means of five circles,i.e.the Arctic and Antarctic, the two tropics, and the equator; that the latter circle is cut obliquely by the ecliptic, and perpendicularly by the meridian. Up to his time no division of the sphere had been made beyond the description of the constellations. These opinions do not appear to have been rapidly spread, since Herodotus, one of the finest intellects of Greece, who lived two centuries later, was still so ill-instructed as to say, in speaking of an eclipse, "The sun abandoned its place, and night took the place of day."
Anaxagoras, of whom we have spoken before, asserted that the sun was a mass of fire larger than the Peloponnesus. Plutarch says he regarded it as a burning stone, and Diogenes Laertius looked upon it as hot iron. For this bold idea he was persecuted. They considered it a crime that he taught the causes of the eclipses of the moon, and pretended that the sun is larger than it looks. He first taught the existence of one God, and he was taxed with impiety and treason against his country. When he was condemned to death, "Nature," he said, "has long ago condemned me to the same; and as to my children, when I gave them birth I had no doubt but they would have to die some day." His disciple Pericles, however, defended him so eloquently that his life was spared, and he was sent into exile.
Pythagoras, who belonged to the school of Thales, and who travelled in Phœnicia, Chaldea, Judæa, and Egypt, to learn their ideas, ventured, in spite of the warnings of the priests, to submit to the rites of initiation at Heliopolis, and thence returned to Samos, but meeting with poor reception there, he went to Italy to teach. From him arose theItalian School, and his disciples took the name of philosophers (lovers of wisdom) instead of that of sages. We shall learn more about him in the chapter on the Harmony of the Spheres.
His first disciple, Empedocles, famous for the curiosity which led him to his death in the crater of Ætna, as the story goes, thought that the true sun, the fire that is in thecentre of the universe, illuminated the other hemisphere, and that what we see is only the reflected image of that, which is invisible to us, and all of whose movements it follows.
His disciple, Philolaus, also taught that the sun was a mass of glass, which sent us by reflection all the light that it scattered through the universe. We must not, however, forget that these opinions are recorded by historians who probably did not understand them, and who took in the letter what was only intended for a comparison or figure.
If we are to believe Plutarch, Xenophanes, who flourished about 360B.C., was very wild in his opinions. He thought the stars were lighted every night and extinguished every morning; that the sun is a fiery cloud; that eclipses take place by the sun being extinguished and afterwards rekindled; that the moon is inhabited, but is eighteen times larger than the earth; that there are several suns and several moons for giving light to different countries. This can only be matched by those who said the sun went every night through a hole in the earth round again to the east; or that it went above ground, and if we did not see it going back it was because it accomplished the journey in the night.
Parmenidas was the disciple of Xenophanes. He divided the earth, like Thales, into zones; and he added that it was suspended in the centre of the universe, and that it did not fall because there was no reason why it should move in one direction rather than another. This argument is perfectlyphilosophical, and illustrates a principle employed since the time of Archimedes, and of which Leibnitz made so much use.
Such are some of the general ideas which were held by the Greeks and others on the nature of the heavens, omitting that of Ptolemy, of which we shall give a fuller account hereafter. We see that they were all affected by the dominant idea of the superiority of the earth over the rest of the universe, and were spoiled for want of the grand conception of the immensity of space. The universe was for them a closed space, outside of which there wasnothing; and they busied themselves with metaphysical questions as to the possibility of space being infinite. In the meantime their conceptions of the distances separating us from other visible parts of the universe were excessively cramped. Hesiod, for instance, thinks to give a grand idea of the size of the universe by saying that Vulcan's anvil took seven days to fall from heaven to earth, when in reality, as now calculated, it would take no less than seventy-two years for the light, even travelling at a far greater rate, to reach us from one of the nearest of the fixed stars.
Nature presents herself to us under various aspects. At times, it may be, she presents to us the appearance of discord, and we fail to perceive the unity that pervades the whole of her actions. At others, however, and most often to an instructed mind, there is a concord between her various powers, a harmony even in her sounds, that will not escape us. Even the wild notes of the tempest and the bass roll of the thunder form themselves into part of the grand chorus which in the great opera are succeeded by the solos of the evening breeze, the songs of birds, or the ripple of the waves. These are ideas that would most naturally present themselves to contemplative minds, and such must have been the students of the silent, but to them harmonious and tuneful, star-lit sky, under the clear atmosphere of Greece. The various motions they observed became indissolubly connected in their minds with music, and they did not doubt that the heavenly spheres made harmony, if imperceptible to humanears. But their ideas were more precise than this. They discovered that harmony depended on number, and they attempted to prove that whether the music they might make were audible or not, the celestial spheres had motions which were connected together in the same way as the numbers belonging to a harmony. The study of their opinions on this point reveals some very curious as well as very interesting ideas. We may commence by referring to an ancient treatise by Timæus of Locris on the soul of the universe. To him we owe the first serious exposition of the complete harmonic cosmography of Pythagoras. We must premise that, according to this school, God employed all existing matter in the formation of the universe—so that it comprehends all things, and all is in it. "It is a unique, perfect, and spherical production, since the sphere is the most perfect of figures; animated and endowed with reason, since that which is animated and endowed with reason is better than that which is not."
So begins Timæus, and then follows, as a quotation from Plato, a comparison of the earth to what would appear to us nowadays to be a very singular animal. Not only, says Plato, is the earth a sphere, but this sphere is perfect, and its maker took care that its surface should be perfectly uniform for many reasons. The universe in fact has no need of eyes, since there is nothing outside of it to see; nor yet of ears, since there is nothing but what is part of itself tomake a sound; nor of breathing organs, as it is not surrounded by air: any organ that should serve to take in nourishment, or to reject the grosser parts, would be absolutely useless, for there being nothing outside it, it could not receive or reject anything. For the same reason it needs no hands with which to defend itself, nor yet of feet with which to walk. Of the seven kinds of motion, its author has given it that which is most suitable for its figure in making it turn about its axis, and since for the execution of this rotatory motion no arms or legs are wanted, its maker gave it none.
With regard to the soul of the universe, Plato, according to Timæus, says that God composed it "of a mixture of the divisible and indivisible essences, so that the two together might be united into one, uniting two forces, the principles of two kinds of motion, one that which isalways the same, and the other that which isalways changing. The mixture of these two essences was difficult, and was not accomplished without considerable skill and pains. The proportions of the mixture were according to harmonic numbers, so chosen that it is possible to know of what, and by what rule, the soul of the universe is compounded."
By harmonic numbers Timæus means those that are proportional to those representing the consonances of the musical scale. The consonances known to the ancients were three in number: the diapason, or octave, in the proportion of2 to 1, the diapent, or fifth, in that of 3 to 2, and the diatessaron, or fourth, in that of 4 to 3; when to these are joined the tones which fill the intervals of the consonances, and are in the proportion of 9 to 8, and the semitones in that of 256 to 243, all the degrees of the musical scale is complete.
The discovery of these harmonic numbers is due to Pythagoras. It is stated that when passing one day near a forge, he noticed that the hammers gave out very accurate musical concords. He had them weighed, and found that of those which sounded the octave, one weighed twice as much as the other; that of those which made a perfect fifth, one weighed one third more than the other, and in the case of a fourth, one quarter more. After having tried the hammers, he took a musical string stretched with weights, and found that when he had applied a given weight in the first instance to make any particular note, he had to double the weight to obtain the octave, to add one third extra only to obtain a fifth, a quarter for the fourth, and eight for one tone, and about an eighteenth for a half-tone; or more simply still, he stretched a cord once for all, and then when the whole length sounded any note, when stopped in the middle it gave the octave, at the third it gave the fifth, at the quarter the fourth, at the eighth the tone, and at the eighteenth the semi-tone.
Since the ancients conceived of the soul by means of motion, the quantity of motion developed in anything was their measure of the quantity of its soul. Now the motion ofthe heavenly bodies seemed to them to depend on their distance from the centre of the universe, the fastest being those at the circumference of the whole. To determine the relative degrees of velocity, they imagined a straight line drawn outwards from the centre of the earth, as far as the empyreal heaven, and divided it according to the proportions of the musical scale, and these divisions they called the harmonic degrees of the soul of the universe. Taking the earth's radius for the first number, and calling it unity, or, in order to avoid fractions, denoting it by 384, the second degree, which is at the distance of an harmonic third, will be represented by 384 plus its eighth part, or 432. The third degree will be 432, plus its eighth part, or 486. The fourth, being a semitone, will be as 243 to 256, which will give 512; and so on. The eighth degree will in this way be the double of 384 or 768, and represents the first octave.
They continued this series to 36 degrees, as in the following table:—
The Earth.