Gore John Ellard
Astronomical Curiosities: Facts and Fallacies
Among other remarkable things contained in Al-Sufi’s most interesting work may be mentioned the great nebula in Andromeda, which was first noticed in Europe as visible to the naked eye by Simon Marius in 1612. Al-Sufi, however, speaks of it as a familiar object in his time.
Schjellerup says —
“For a long time many of the stars in Ptolemy’s catalogue could not be identified in the sky. Most of these discordances were certainly due to mistakes in copying, either in longitude or latitude. Many of these differences were, however, corrected by the help of new manuscripts. For this purpose Al-Sufi’s work is of great importance. By a direct examination of the sky he succeeded in finding nearly all the stars reported by Ptolemy (or Hipparchus). And even if his criticism may sometimes seem inconclusive, his descriptions are not subject to similar defects, his positions not depending solely on the places given in Ptolemy’s catalogue. For, in addition to the longitudes and latitudes quoted from Ptolemy, he has described by alignment the positions of the stars referred to. In going from the brightest and best known stars of each constellation he indicates the others either by describing some peculiarity in their position, or by giving their mutual distance as so many cubits (dzirâ), or a span (schibr), units of length which were used at that time to measure apparent celestial distances. The term dzirâ means literally the fore-arm from the bone of the elbow to the tip of the middle finger, or an ell. We should not, however, conclude from this that the Arabians were so unscientific as to measure celestial distances by an ell, as this would be quite in contradiction to their well-known knowledge of Geometry and Trigonometry.”
With reference to the arc or angular distance indicated by the “cubit,” Al-Sufi states in his description of the constellation Auriga that the dzirâ (or cubit) is equal to 2° 20′. Three cubits, therefore, represent 7°, and 4 cubits 9° 20′.
In Al-Sufi’s own preface to his work, after first giving glory to God and blessings on “his elected messenger Muhammed and his family,” he proceeds to state that he had often “met with many persons who wished to know the fixed stars, their positions on the celestial vault, and the constellations, and had found that these persons may be divided into two classes. One followed the method of astronomers and trust to spheres designed by artists, who not knowing, the stars themselves, take only the longitudes and latitudes which they find in the books, and thus place the stars on the sphere, without being able to distinguish truth from error. It then follows that those who really know the stars in the sky find on examining these spheres that many stars are otherwise than they are in the sky. Among these are Al-Battani, Atârid and others.”
Al-Sufi seems rather hard on Al-Battani (or Albategnius as he is usually called) for he is generally considered to have been the most distinguished of the Arabian astronomers. His real name was Mohammed Ibn Jaber Ibn Senan Abu Abdallah Al-Harrani. He was born about A.D. 850 at Battan, near Harran in Mesopotamia, and died about A.D. 929. He was the first to make use of sines instead of chords, and versed sines. The Alphonsine Tables of the moon’s motions were based on his observations.
After some severe criticisms on the work of Al-Battani and Atârid, Al-Sufi goes on to say that the other class of amateurs who desire to know the fixed stars follow the method of the Arabians in the science of Anva391 and the mansions of the moon and the books written on this subject. Al-Sufi found many books on the anva, the best being those of Abu Hanifa al-Dînavari. This work shows that the author knew the Arabic tradition better than any of the other writers on the subject. Al-Sufi, however, doubts that he had a good knowledge of the stars themselves, for if he had he would not have followed the errors of his predecessors.
According to Al-Sufi, those who know one of these methods do not know the other. Among these is Abu-Hanifa, who states in his book that the names of the twelve signs (of the Zodiac) did not originate from the arrangement or configuration of the stars resembling the figure from which the name is derived. The stars, Abu-Hanifa said, “change their places, and although the names of the signs do not change, yet the arrangement of the stars ceases to be the same. This shows that he was not aware of the fact that the arrangement of the stars does not change, and their mutual distances and their latitudes, north and south of the ecliptic, are neither increased nor diminished.” “The stars,” Al-Sufi says, “do not change with regard to their configurations, because they are carried along together by a physical motion and by a motion round the poles of the ecliptic. This is why they are called fixed. Abu-Hanifa supposed that they are termed fixed because their motion is very slow in comparison with that of the planets.” “These facts,” he says, “can only be known to those who follow the method of the astronomers and are skilled in mathematics.”
Al-Sufi says that the stars of the Zodiac have a certain movement following the order of the signs, which according to Ptolemy and his predecessors is a degree in 100 years. But according to the authors of al-mumtahan and those who have observed subsequently to Ptolemy, it is a degree in 66 years. According to modern measures, the precession is about 50″·35 per annum, or one degree in 71½ years.
Al-Sufi says that the Arabians did not make use of the figures of the Zodiac in their proper signification, because they divided the circumference of the sky by the number of days which the moon took to describe it – about 28 days – and they looked for conspicuous stars at intervals which, to the eye, the moon appeared to describe in a day and a night. They began with al-scharataïn, “the two marks” (α and β Arietis) which were the first striking points following the point of the spring equinox. They then sought behind these two marks another point at a distance from them, equal to the space described by the moon in a day and a night. In this way they found al-butaïn (ε, δ, and ρ Arietis); after that al-tsuraija, the Pleiades; then al-dabaran, the Hyades, and thus all the “mansions” of the moon. They paid no attention to the signs of the Zodiac, nor to the extent of the figures which composed them. This is why they reckoned among the “mansions” al-haka (λ Orionis) which forms no part of the signs of the Zodiac, since it belongs to the southern constellation of the Giant (Orion). And similarly for other stars near the Zodiac, of which Al-Sufi gives some details. He says that Regulus (α Leonis) was called by the Arabians al-maliki, the Royal Star, and that al-anva consists of five stars situated in the two wings of the Virgin. These stars seem to be β, η, γ, δ, and ε Virginis, which form with Spica (α Virginis) a Y-shaped figure. Spica was called simak al-azal, the unarmed simak; the “armed simak” being Arcturus, simak al-ramih. These old Arabic names seem very fanciful.
Al-Sufi relates that in the year 337 of the Hegira (about A.D. 948) he went to Ispahan with Prince Abul-fadhl, who introduced him to an inhabitant of that city, named Varvadjah, well known in that country, and famous for his astronomical acquirements. Al-Sufi asked him the names of the stars on an astrolabe which he had, and he named Aldebaran, the two bright stars in the Twins (Castor and Pollux), Regulus, Sirius, and Procyon, the two Simaks, etc. Al-Sufi also asked him in what part of the sky Al-fard (α Hydræ) was, but he did not know! Afterwards, in the year 349, this same man was at the court of Prince Adhad-al-Davlat, and in the presence of the Prince, Al-Sufi asked him the name of a bright star – it was al-nasr al-vaki, the falling Vulture (Vega), and he replied, “That is al-aijuk” (Capella)! thus showing that he only knew the names of the stars, but did not know them when he saw them in the sky. Al-Sufi adds that all the women “who spin in their houses” knew this star (Vega) by the name of al-atsafi, the Tripod. But this could not be said even of “educated women” at the present day.
With reference to the number of stars which can be seen with the naked eye, Al-Sufi says, “Many people believe that the total number of fixed stars is 1025, but this is an evident error. The ancients only observed this number of stars, which they divided into six classes according to magnitude. They placed the brightest in the 1st magnitude; those which are a little smaller in the 2nd; those which are a little smaller again in the 3rd; and so on to the 6th. As to those which are below the 6th magnitude, they found that their number was too great to count; and this is why they have omitted them. It is easy to convince one’s self of this. If we attentively fix our gaze on a constellation of which the stars are well known and registered, we find in the spaces between them many other stars which have not been counted. Take, for example, the Hen [Cygnus]; it is composed of seventeen internal stars, the first on the beak, the brightest on the tail, the others on the wings, the neck and the breast; and below the left wing are two stars which do not come into the figure. Between these different stars, if you examine with attention, you will perceive a multitude of stars, so small and so crowded that we cannot determine their number. It is the same with all the other constellations.” These remarks are so correct that they might have been written by a modern astronomer. It should be added, however, that all the faint stars referred to by Al-Sufi – and thousands of others still fainter – have now been mapped down and their positions accurately determined.
About the year 1437, Ulugh Beigh, son of Shah Rokh, and grandson of the Mogul Emperor Tamerlane, published a catalogue of stars in which he corrected Ptolemy’s positions. But he seems to have accepted Al-Sufi’s star magnitudes without any attempt at revision. This is unfortunate, for an independent estimate of star magnitudes made in the fifteenth century would now be very valuable for comparison with Al-Sufi’s work and with modern measures. Ulugh Beigh’s catalogue contains 1018 stars, nearly the same number as given by Ali-Sufi.392
CHAPTER XIX
The Constellations393
Curious to say, Al-Sufi rated the Pole Star as 3rd magnitude; for it is now only slightly less than the 2nd. At present it is about the same brightness as β of the same constellation (Ursa Minor) which Al-Sufi rated 2nd magnitude. It was, however, also rated 3rd magnitude by Ptolemy (or Hipparchus), and it may possibly have varied in brightness since ancient times. Admiral Smyth says that in his time (1830) it was “not even a very bright third size” (!)394 Spectroscopic measures show that it is approaching the earth at the rate of 16 miles a second; but this would have no perceptible effect on its brightness in historical times. This may seem difficult to understand, and to some perhaps incredible; but the simple explanation is that its distance from the earth is so great that a journey of even 2000 years with the above velocity would make no appreciable difference in its distance! This is undoubtedly true, as a simple calculation will show, and the fact will give some idea of the vast distance of the stars. The well-known 9th magnitude companion to the Pole Star was seen by day in the Dorpat telescope by Struve and Wrangel; and “on one occasion by Encke and Argelander.”395
The star β Ursæ Minoris was called by the Arabians Kaukab al-shamáli, the North Star, as it was – owing to the precession of the Equinoxes – nearer to the Pole in ancient times than our present Pole Star was then.
The “Plough” (or Great Bear) is supposed to represent a waggon and horses. “Charles’ Wain” is a corruption of “churl’s wain,” or peasant’s cart. The Arabians thought that the four stars in the quadrilateral represented a bier, and the three in the “tail” the children of the deceased following as mourners! In the Greek mythology, Ursa Major represented the nymph Callisto, a daughter of Lycaon, who was loved by Jupiter, and turned into a bear by the jealous Juno. Among the old Hindoos the seven stars represented the seven Rishis. It is the Otawa of the great Finnish epic, the “Kalevala.” It was also called “David’s Chariot,” and in America it is known as “The Dipper.”
Closely north of the star θ in Ursa Major is a small star known as Flamsteed 26. This is not mentioned by Al-Sufi, but is now, I find from personal observation, very visible, and indeed conspicuous, to the naked eye. I find, however, that owing to the large “proper motion” of the bright star (1″·1 per annum) the two stars were much closer together in Al-Sufi’s time than they are at present, and this probably accounts for Al-Sufi’s omission. This is an interesting and curious fact, and shows the small changes which occur in the heavens during the course of ages.
Close to the star ζ, the middle star of the “tail” of Ursa Major (or handle of the “Plough”), is a small star known as Alcor, which is easily visible to good eyesight without optical aid. It is mentioned by Al-Sufi, who says the Arabians called it al-suha, “the little unnoticed one.” He says that “Ptolemy does not mention it, and it is a star which seems to test the powers of the eyesight.” He adds, however, an Arabian proverb, “I show him al-suha, and he shows me the moon,” which seems to suggest that to some eyes, at least, it was no test of sight at all. It has, however, been suspected of variation in light. It was rated 5th magnitude by Argelander, Heis, and Houzeau, but was measured 4·02 at Harvard Observatory. It has recently been found to be a spectroscopic binary.
The constellation of the Dragon (Draco) is probably referred to in Job (chap. xxvi. v. 13), where it is called “the crooked serpent.” In the Greek mythology it is supposed to represent the dragon which guarded the golden apples in the Garden of the Hesperides. Some have suggested that it represented the serpent which tempted Eve. Dryden says, in his translation of Virgil —
“Around our Pole the spiry Dragon glides,
And like a wand’ring stream the Bears divides.”
The fact that the constellation Boötis rises quickly and sets slowly, owing to its lying horizontally when rising and vertically when setting, was noted by Aratus, who says —
“The Bearward now, past seen,
But more obscured, near the horizon lies;
For with the four Signs the Ploughman, as he sinks,
The deep receives; and when tired of day
At even lingers more than half the night,
When with the sinking sun he likewise sets
These nights from his late setting bear their name.”396
The cosmical setting of Boötis – that is, when he sets at sunset – is stated by Ovid to occur on March 5 of each year.
With reference to the constellation Hercules, Admiral Smyth says —
“The kneeling posture has given rise to momentous discussion; and whether it represents Lycaon lamenting his daughter’s transformation, or Prometheus sentenced, or Ixion ditto, or Thamyrus mourning his broken fiddle, remains still uncertain. But in process of time, this figure became a lion, and Hyginus mentions both the lion’s skin and the club; while the right foot’s being just over the head of the Dragon, satisfied the mythologists that he was crushing the Lernæan hydra… Some have considered the emblem as typifying the serpent which infested the vicinity of Cape Tænarus, whence a sub-genus of Ophidians still derives its name. At all events a poet, indignant at the heathen exaltation of Hevelius, has said —
“‘To Cerberus, too, a place is given —
His home of old was far from heaven.’”397
Aratus speaks of Hercules as “the Phantom whose name none can tell.”
There were several heroes of the name of Hercules, but the most famous was Hercules the Theban, son of Jupiter and Alcmene wife of Amphitryon, King of Thebes, who is said to have lived some years before the siege of Troy, and went on the voyage of the Argonauts about 1300 B.C. According to some ancient writers, another Hercules lived about 2400 B.C., and was a contemporary of Atlas and Theseus. But according to Pétau, Atlas lived about 1638 B.C., and Lalande thought that this chronology is the more probable.
The small constellation Lyra, which contains the bright star Vega, is called by Al-Sufi the Lyre, the Goose, the Persian harp, and the Tortoise. In his translation of Al-Sufi’s work, Schjellerup suggests that the name “Goose” may perhaps mean a plucked goose, which somewhat resembles a Greek lyre, and also a tortoise. The name of the bright star Vega is a corruption of the Arabic vâki. Ptolemy and Al-Sufi included all the very brightest stars in the “first magnitude,” making no distinction between them, but it is evident at a glance that several of them, such as Arcturus and Vega, are brighter than an average star of the first magnitude, like Aldebaran.
The constellation Perseus, which lies south-east of “Cassiopeia’s Chair,” may be recognized by the festoon formed by some of its stars, the bright star α Persei being among them. It is called by Al-Sufi “barschânsch, Περσεύς, Perseus, who is hamil râs al-gul, the Bearer of the head of al-gul.” According to Kazimirski, “Gul was a kind of demon or ogre who bewilders travellers and devours them, beginning at the feet. In general any mischievous demon capable of taking all sorts of forms.” In the Greek mythology Perseus was supposed to be the son of Jupiter and Danæ. He is said to have been cast into the sea with his mother and saved by King Polydectus. He afterwards cut off the head of Medusa, one of the Gorgons, while she slept, and armed with this he delivered Andromeda from the sea-monster.
The constellation Auriga lies east of Perseus and contains the bright star Capella, one of the three brightest stars in the northern hemisphere (the others being Arcturus and Vega). Theon, in his commentary on Aratus, says that Bellerophon invented the chariot, and that it is represented in the heavens by Auriga, the celestial coachman. According to Dupuis, Auriga represents Phæton, who tried to drive the chariot of the sun, and losing his head fell into the river Eridanus. The setting of Eridanus precedes by a few minutes that of Auriga, which was called by some of the ancient writers Amnis Phaï-tontis.398 Auriga is called by Al-Sufi numsick al-ainna– He who holds the reins, the Coachman; also al-inâz, the She-goat. M. Dorn found in Ptolemy’s work, the Greek name ‘Ηνίοχοι, Auriga, written in Arabic characters. Al-Sufi says, “This constellation is represented by the figure of a standing man behind ‘He who holds the head of al-gûl’ [Perseus], and between the Pleiades and the Great Bear.”
Capella is, Al-Sufi says, “the bright and great star of the first magnitude which is on the left shoulder [of the ancient figure] on the eastern edge of the Milky Way. It is that which is marked on the astrolabe as al-aijûk.” The real meaning of this name is unknown. Schjellerup thought, contrary to what Ideler says, that the name is identical with the Greek word Αϊξ (a goat). Capella was observed at Babylon about 2000 B.C., and was then known as Dilgan. The Assyrian name was Icu, and the Persian name colca. It was also called Capra Hircus, Cabrilla, Amalthea, and Olenia. In ancient times the rising of Capella was supposed to presage the approach of storms. Ovid says, “Olenia sidus pluviale Capellæ.”
The constellation Aquila is called by Al-Sufi al-ukab, the Eagle, or al-nasr al-tâïr, the flying vulture. According to the ancient poets the eagle carried nectar to Jupiter when he was hidden in a cave in Crete. This eagle also assisted Jupiter in his victory over the Giants and contributed to his other pleasures. For these reasons the eagle was consecrated to Jupiter, and was placed in the sky. Al-Sufi says, “There are in this figure three famous stars [γ, α, and β Aquilæ], which are called al-nasr al-tâïr.” Hence is derived the modern name Altair for the bright star α Aquilæ. Al-Sufi says that the “common people” call “the three famous stars” al-mîzân, the Balance, on account of the equality of the stars.” This probably refers to the approximately equal distances between γ and α, and α and β, and not to their relative brightness. He says “Between the bright one of the tail [ξ Aquilæ] and the star in the beak of the Hen [β Cygni] in the thinnest part of the Milky Way, we see the figure of a little earthen jar, of which the stars begin at the bright one in the tail, and extend towards the north-west. [This seems to refer to ε Aquilæ and the small stars near it.] They then turn towards the east in the base of the jar, and then towards the south-east to a little cloud [4, 5, etc. Vulpeculæ, a well-known group of small stars] which is found to the north of the two stars in the shaft of the Arrow [α and β Sagittæ]. The cloud is on the eastern edge of the jar, and the bright one on the tail on the western edge; the orifice is turned towards the flying Vulture [Aquila], and the base towards the north. Among these are distinguished some of the fourth, fifth, and sixth magnitudes [including, probably, 110, 111, 112, 113 Hercules, and 1 Vulpeculæ] and Ptolemy says nothing of this figure, except the bright star in the tail of the Eagle” (see figure). The above is a good example of the minute accuracy of detail in Al-Sufi’s description.
The southern portion of Aquila was formerly called Antinous, who was said to have been a young man of great beauty born at Claudiopolis in Bithynia, and drowned in the Nile. Others say that he sacrificed his life to save that of the Emperor Hadrian, who afterwards raised altars in his honour and placed his image on coins.399
The constellation Pegasus, Al-Sufi says, “is represented by the figure of a horse, which has the head, legs, and forepart of the body to the end of the back, but it has neither hind quarters nor hind legs.” According to Brown, Pegasus was the horse of Poseidon, the sea god. Half of it was supposed to be hidden in the sea, into which the river Eridanus flowed.400 In the Greek mythology it was supposed to represent the winged horse produced by the blood which fell from the head of Medusa when she was killed by Perseus! Some think that it represents Bellerophon’s horse, and others the horse of Nimrod. It was also called Sagmaria and Ephippiatus, and was sometimes represented with a saddle instead of wings.
In describing the constellation Andromeda, Al-Sufi speaks of two series of stars which start from the great nebula in Andromeda; one series going through 32 Andromedæ, π, δ, and ε to ζ and η; and the other through ν, μ, β Andromedæ into the constellation Pisces. He says they enclose a fish-shaped figure called by the Arabians al-hût, the Fish, par excellence. He speaks of two other series of stars which begin at τ and υ, and diverging meet again at χ Persei, forming another “fish-like figure.” The eastern stream starts from τ and passes through 55, γ, 60, 62, 64, and 65 Andromedæ; and the western stream from υ through χ 51, 54, and g Persei up to χ Persei. The head of the first “fish,” al-hût, is turned towards the north, and that of the second towards the south (see figure).
Al-Sufi says that the stars α Persei, γ, β, δ, and α Andromedæ, and β Pegasi form a curved line. This is quite correct, and this fine curve of bright stars may be seen at a glance on a clear night in September, when all the stars are high in the sky.
The first constellation of the Zodiac, Aries, the Ram, was called, according to Aratus and Eratosthenes, κρίος. It is mentioned by Ovid under the name of Hellas. It was also called by the ancients the Ram with the golden horns. Manilius (fourth century B.C.) called it “The Prince.” It is supposed to have represented the god Bel. Among the Accadians the sign meant “He who dwells on the altar of uprightness.” It first appears on the Egyptian Zodiac; and it was sacred to Jupiter Ammon. In the Greek mythology it was supposed to represent the ram, the loss of whose fleece led to the voyage of the Argonauts. In the time of Hipparchus, about 2000 years ago, it was the first sign of the Zodiac, or that in which the sun is situated at the Vernal Equinox (about March 21 in each year). But owing to the precession of the equinoxes, this point has now moved back into Pisces.
The brightest star of Aries (α) is sometimes called Hamal, derived from the Arabic al-hamal, a name given to the constellation itself by Al-Sufi. In the Accadian language it was called Dilkur, “the dawn proclaimer.” Ali-Sufi says that close to α, “as if it were attached to it,” is a small star of the 6th magnitude, not mentioned by Ptolemy. This is clearly κ Arietis. The fact of Al-Sufi having seen and noticed this small star, which modern measures show to be below the 5th magnitude, is good evidence of his keen eyesight and accuracy of observation.
According to Al-Sufi, the stars β and γ Arietis were called by the Arabians al-scharatain, “the two marks.” They marked the “first mansion of the moon,” and ε, δ, and ρ the second mansion. With reference to these so-called “mansions of the moon,” Admiral Smyth says —
“The famous Manazil al-kamar, i.e. Lunar mansions, constituted a supposed broad circle in Oriental astronomy divided into twenty-eight unequal parts, corresponding with the moon’s course, and therefore called the abodes of the moon. This was not a bad arrangement for a certain class of gazers, since the luminary was observed to be in or near one or other of these parts, or constellations every night. Though tampered with by astrologers, these Lunar mansions are probably the earliest step in ancient astronomy.”401
Taurus, the second constellation of the Zodiac, was in ancient times represented by the figure of a bull, the hinder part of which is turned towards the south-west, and the fore part towards the east. It had no hind legs, and the head was turned to one side, with the horns extended towards the east. Its most ancient name was Te, possibly a corruption of the Accadian dimmena, “a foundation-stone.” The Greek name is ἀθώρ (θωώρ, Eusebius). In the old Egyptian mythology Taurus represented the god Apis. According to Dupuis it also represented the 10th “labour of Hercules,” namely, his victory over the cows of Geryon, King of Spain.402 It was also supposed to represent the bull under the form of which Jupiter carried off Europa, daughter of Agenor, King of the Phœnicians. It may also refer to Io or Isis, who is supposed to have taught the ancient Egyptians the art of agriculture.
Aldebaran is the well-known bright red star in the Hyades. It was called by Ptolemy Fulgur succularum. Ali-Sufi says it was marked on the old astrolabes as al-dabaran, “the Follower” (because it follows the Hyades in the diurnal motion), and also ain al-tsaur, the eye of the bull. It may be considered as a standard star of the 1st magnitude. Modern observations show that it has a parallax of 0″·107. It is receding from the earth, according to Vogel, at the rate of about 30 miles a second; but even with this high velocity it will take thousands of years before its brightness is perceptibly diminished. It has a faint companion of about the 10th magnitude at the distance of 118″, which forms a good “light test” for telescopes of 3 or 4 inches aperture. I saw it well with a 4-inch Wray in the Punjab sky. The Hyades were called Succulæ by the Romans, and in the Greek mythology were said to be children of Atlas.
The star β Tauri, sometimes called Nath, from the Arabic al-nátih, the butting, is a bright star between Capella and γ Orionis (Bellatrix). It is on the tip of the horn in the ancient figure of Taurus, and “therefore” (says Admiral Smyth) “at the greatest distance from the hoof; can this have given rise to the otherwise pointless sarcasm of not knowing B from a bull’s foot?”403 Al-Sufi says that an imaginary line drawn from the star now known as A Tauri to τ Tauri would pass between υ and κ Tauri, which is quite correct, another proof of the accuracy of his observations. He also says that the star ω Tauri is exactly midway between A and ε, which is again correct. He points out that Ptolemy’s position of ω is incorrect. This is often the case with Ptolemy’s positions, and tends to show that Ptolemy adopted the position given by Hipparchus without attempting to verify their position in the sky. Al-Sufi himself adopts the longitudes and latitudes of the stars as given by Ptolemy in the Almagest, but corrects the positions in his descriptions, when he found Ptolemy’s places erroneous.
The famous group of the Pleiades is well known; but there is great difficulty in understanding Al-Sufi’s description of the cluster. He says, “The 29th star (of Taurus) is the more northern of the anterior side of the Pleiades themselves, and the 30th is the southern of the same side; the 31st is the following vertex of the Pleiades, and is in the more narrow part. The 32nd is situated outside the northern side. Among these stars, the 32nd is of the 4th magnitude, the others of the 5th.” Now, it is very difficult or impossible to identify these stars with the stars in the Pleiades as they are at present. The brightest of all, Alcyone (η Tauri), now about 3rd magnitude, does not seem to be mentioned at all by Al-Sufi! as he says distinctly that “the brightest star” (№ 32 of Taurus) is “outside” the Pleiades “on the northern side.” It seems impossible to suppose that Al-Sufi could have overlooked Alcyone had it the same brightness it has now. The 32nd star seems to have disappeared, or at least diminished greatly in brightness, since the days of Al-Sufi. More than four stars were, however, seen by Al-Sufi, for he adds, “It is true that the stars of the Pleiades must exceed the four mentioned above, but I limit myself to these four because they are very near each other and the largest [that is, the brightest]; this is why I have mentioned them, neglecting the others.” A full examination of the whole question is given by Flammarion in his interesting work Les Étoiles (pp. 289-307), and I must refer my readers to this investigation for further details.