Hic Sunt Dracones:1 Why Are There Dragons on Medieval Astrolabes?
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Hic Sunt Dracones:1 Why are there dragons on medieval astrolabes? John Davis One of the many delights of researching medi- eval astrolabes is that the star pointers on their retes are often zoomorphic. In particular, the two ends of its outer frame (the Capricornian ring) are sometimes fashioned as the head and tail of a dragon – see Fig. 1 for an example. Whilst the use of a dog’s head as the pointer for the Dog star Sirius (αCMa, Alhabor), or birds for the Eagle Altair (α Aql) or the Ra- ven Corvus (g Crv, Algorab) are obviously intended as forms of a rebus or aide-memoire, it is not clear what meaning the dragon is sup- posed to portray. Surprisingly, there have been very few proper studies of this feature with not even a listing of which astrolabes include dragons being published, let alone an accepted hypothesis connecting them with a development of the instrument from the early 14th century on- wards. Owen Gingerich did publish a useful study in 1987 on zoomorphic astrolabes but he was principally interested in the introduc- tion of Arabic star names into the Latin West.2 More recently, Azucena Pérez has made an important contribution to the subject3, point- ing out that the dragons only appear on Chris- tian astrolabes, not on Islamic ones, and that they are not discussed in contemporary manu- script treatises describing the design and use of the instrument, despite the fact that they are actually included in some of the illustrations to Geoffrey Chaucer’s 1391 Treatise on the Astrolabe.4 Instead, she points to contempo- rary astrological and magic treatises which do consider dragons. Other authors have men- tioned the dragons in passing: John North5 Fig. 1 (a) The earliest dated Latin astrolabe ientife them merely s str ointers for the of 1326 includes the head and tail of a stars Calbalacrab (α Sco, Cor Scorpionis) and dragon. British Museum inv. BM 1909 Denebalgedi (d Cap, Cauda Capricorni). Paul 0617.1. Left (b) the dragon’s head. Photos by Kunitzsch6 showed that they might be indica- the author with permission of the Trustees of tors of the Ptolemaic constellation Serpens. the British Museum. i in hs shon them freuently in his extensive astrolabe publications but without a detailed discussion.7 These ideas will be discussed below but it should be pointed out Fig. 2 One of a pair of ‘dragons’ in the that existing explanations are exclusively as- wrought ironwork of the infrmary doors of tronomical and thus may well miss the way in Norwich Cathedral c. 1280. Now in Norwich which medieval minds were working. Castle Museum. A Note on Terminology In Latin, serpens refers to a snake, a real ani- mal sometimes called a serpent in old English, and dracone to the mythical dragon.8 How- ever, these distinctions were not always made and it is often not clear which beast is being indicated – the creature in the 13th-century rouhtironor on the infrmry oors of Norwich Cathedral (Fig. 2) could be either.9 Added to this, there was a variety of differ- ent types of dragon to be found in a medieval bestiary. The true dragon had two pairs of 2 Bulletin of the Scientifc Instrument Society No. 143 (2019) be others to add to the list. The table makes seerl oints frstly the erliest te u- roen scientifc instrument from 132 n now in the British Museum (BM; see Fig. 1), is on the list (no. 1) and hence is the earliest dated appearance of a dragon on the Capri- cornian ring.13 Secondly, the majority of the earliest astrolabes are English but dragons be- came popular on Italian astrolabes from the middle of the fourteenth century, remaining until the beginning of the sixteenth century. Other nations are missing from the list – there are no instruments from Spain or Germany listed and the austere designs from the Pa- risian workshop of Jean Fusoris never have dragons. Thirdly, although the most common confurtion is to he the he of the ron on the right (near Scorpionis/Sagittarius on the ecliptic) and its tail on the left (near Capri- cornusurius) the oosite rrnement is also seen and there are even cases where there are two heads and no tail. These variations are unexplained. It is highly likely that there were a few as- trolabes in England before the BM’s 1326 instrument. For example, Adelard of Bath would have had an astrolabe when he wrote his De Opere Astrolapsus for Henry II in 1142 or 1149.14 And Walcher of Malvern evidently had one (possibly brought from his home location of Lotharingia) for timing the lunar eclipse of 18 October 1092.15 We have no idea whether they included dragons but it seems unlikely as their astrolabes would have followed the Islamic designs gradually being copied in the Latin parts of the Iberian pen- insula. Fig. 3 (a) Vincenzo Danti’s astrolabe, c. Two other astrolabes are thought to have been 1490. After Gunther (ref . 11) Left (b) the made within a year or two of the BM’s 1326 dragon’s head. instrument. One of these is the Great Sloane astrolabe16, also in the BM, and the other is to here generically as dragons. Robert Gun- a very small astrolabe belonging to Gonville ther, though, describes the creatures on Vin- and Caius College, Cambridge, where it has cenzo Danti’s astrolabe (no. 27 in Table 1) spent most of its life.17 All three of these as- as “snakes” despite the fact that both heads trolabes also include calendars on their backs clearly have ears and, on this occasion, the which list a selection of important saints’ or animals have legs too, as can be seen in Fig. fest ys. hey ere the frst to ot this 11 3. Elsewhere, he tends to describe the Eng- feature which became a particularly English lish astrolabes as having “Dragons” whereas trait for the next century and they also all have legs and a pair of wings. The ‘wyvern’ had en inerich clls the fures on the in- connections with East Anglia which will be one pair of legs and wings whilst the ‘wyrm’ swick’ and ‘Blakene’ astrolabes (nos. 12 and discussed further below. The dragon’s head on had neither wings nor legs and hence looked 11 in Table 1 respectively) “serpents” so it the Sloane astrolabe (Fig. 4) is in the left-hand rather like a snake though its breath was said seems there has been little consensus or con- position and is easily overlooked. That on the to be poisonous. Note, though, that dragons 12 sistency amongst modern writers. Ptolemy Caius astrolabe (Fig. 5) is not particularly had (external) ears which real snakes lack. did know the difference and his list of 48 clas- well modelled but is more prominent. One form of ‘dragon’ known as an ‘amphis- sical constellations includes both Draco (in baena’ had a secondary head on its tail which the far northern sky not related to astrolabes) Astrological and Astronomical Origins might account for some of the astrolabe de- and Serpens, on which there is more below. The early references to dragons in an astro- 10 pictions. Both these constellations appear amongst the nomical and/or astrological context come By the nature of the Capricornian ring, the 88 of the modern IAU list. from the Islamic world though the origins are th beasts on astrolabe retes are generally long Which Astrolabes Have Dragons? much earlier. For example, a 12 -century Ar- and thin, lacking legs or wings, but they usu- abic manuscript has a frontispiece miniature Table 1 lists the astrolabes which are known ally have visible ears so they will be referred in which the head and tail of a dragon – ca- to feature dragons on their retes – there may Bulletin of the Scientifc Instrument Society No. 143 (2019) 3 Fig. 4 The rather small dragon on the British Museum great Sloane astrolabe (SL. MathInst 54; #324), dated to c. 1326. Photo by the author, with thanks to the Trustees of the British Museum. put draconis and cauda draconis respectively – stand for the two nodes of the lunar orbit which cut the ecliptic 180° apart.18 These points are the result of the orbit being at ap- proximately 5° to the ecliptic and it is only when the moon is at or very close to these points that an eclipse, either lunar or solar, is possible. The myth that it is a dragon swallow- ing the sun or moon that creates the eclipse goes back to the Babylonian civilisation and, in the middle ages, led to the two nodes being designated as pseudo-planets which appear on eutori n stronomicl tles ith n or- bit of their own. A physical representation of symbolic rep- resentations of the pseudo-planets caput and cauda draconis amongst the other classical planets can be seen on the lid of the famous silver-inlaid bronze ‘Vasa Vescovali’ in the British Museum (Fig. 6).19 The vase dates to c. 1200 and is from Khurasan or possibly Herat (modern Iran and Afghanistan). The lid features eight roundels which contain person- ifctions of the lnets incluin the ron ‘Jawzahr’ who represents the lunar eclipse. An exhibition in New York in 1997 was ex- plicitly arranged to display the images of the zodiac in Islamic art.20 Despite this abundance ir of rons) circle inefnitely sllo- of interest in astrology in the Arab world, it ing its tail. The symbol was later used on the must be stressed that no Islamic astrolabe is 1582 papal medal (Fig.