cercles; of whiche the leste is cleped the cercle of Cancer, bycause that the heved of Cancer turneth evermor consentrik up-on the same cercle. In this heved of Cancer is the grettest declinacioun northward of the sonne. And ther-for is he cleped the 5 Solsticioun of Somer; whiche declinacioun, aftur Ptholome, is 23 degrees and 50 minutes, as wel in Cancer as in Capricorne. This signe of Cancre is cleped the Tropik of Somer, of tropos, that is to seyn 'agaynward;' for thanne by-ginneth the sonne to passe fro us-ward. And for the more declaracioun, lo here the figure.

The middel cercle in wydnesse, of thise 3, is cleped the Cercle Equinoxial; up-on whiche turneth evermo the hedes of Aries and Libra. And understond wel, that evermo this Cercle Equinoxial turneth iustly fro verrey est to verrey west; as I have shewed thee in the spere solide. This same cercle is cleped also the Weyere, 15 equator, of the day; for whan the sonne is in the hevedes of Aries and Libra, than ben the dayes and the nightes ilyke of lengthe in al the world. And ther-fore ben thise two signes called the Equinoxies. And alle that moeveth with-in the hevedes of thise Aries and Libra, his moeving is cleped north- 20 ward; and alle that moeveth with-oute thise hevedes, his moeving.

dropped in under the Rete is that shewn in fig. 5, Plate III, and which Chaucer now describes. Any number of these, marked differently for different latitudes, could be provided for the Astrolabe. The greatest declination of the sun measures the obliquity of the ecliptic, the true value of which is slightly variable, but was about 23° 31′ in Chaucer's time, and about 23° 40′ in the time of Ptolemy, who certainly assigns to it too large a value. The value of it must be known before the three circles can be drawn. The method of finding their relative magnitudes is very simple. Let ABCD (fig. 8, Pl. IV) be the tropic of Capricorn, BO the South line, OC the West line. Make the angle EOB equal to the obliquity (say 234°), and join EA, meeting BO in F. Then OF is the radius of the Equatorial circle, and if GH be drawn parallel to EF, OH is the radius of the Tropic of Cancer. In the phrase angulus primi motus, angulus must be taken to mean angular motion. The 'first moving' (primus motus) has its name of 'moving' (motus) from its denoting motion due to the primum mobile or 'first moveable.' This primum mobile (usually considered as the ninth sphere) causes the rotation of the eighth sphere, or sphæra stellarum fixarum. See the fig. in MS. Camb. Univ. Ii. 3. 3 (copied in fig. 10, Pl. V). Some authors make 12 heavens, viz. those of the 7 planets, the firmamentum (stellarum fixarum), the nonum cœlum, decimum cœlum, primum mobile, and cælum empyræum.

is cleped south-ward as fro the equinoxial. Tak keep of thise latitudes north and sowth, and forget it nat.

By this Cercle Equinoxial ben considered the 24 houres of the clokke; for 25 everemo the arysing of 15 degrees of the equinoxial maketh an houre equal of the clokke. This equinoxial is cleped the girdel of the firste moeving, or elles of the angulus primi motus vel primi mobilis. And nota, that firste moeving is cleped 'moeving' of the firste moevable of the 8 spere, whiche moeving is fro est to 30 west, and eft agayn in-to est; also it is clepid 'girdel' of the first moeving, for it departeth the firste moevable, that is to seyn, the spere, in two ilyke parties, evene-distantz fro the poles of this world.

The wydeste of thise three principal cercles is cleped the 35 Cercle of Capricorne, by-cause that the heved of Capricorne turneth evermo consentrik up-on the same cercle. In the heved of this for-seide Capricorne is the grettest declinacioun southward of the sonne, and ther-for is it cleped the Solsticioun of Winter. This signe of Capricorne is also cleped the Tropik of Winter, for 40 thanne byginneth the sonne to come agayn to us-ward. And for the more declaracioun, lo here thy figure.

18. Upon this forseide plate ben compassed certein cercles that highten Almicanteras, of which som of hem semen perfit cercles, and somme semen inperfit. The centre that standith a-middes the narwest cercle is cleped the Senith; and the 5 netherest cercle, or the firste cercle, is clepid the Orisonte, that is to seyn, the cercle that devydeth the two emisperies, that is, the partie of the hevene a-bove the erthe and the partie be-nethe. Thise Almicanteras ben compowned by two and two, al-be-it so that on divers Astrolabies some Almicanteras ben devyded by oon, 10 and some by two, and somme by three, after the quantite of the Astrolabie. This forseide senith is imagened to ben the verrey point over the crowne of thyn heved; and also this senith is the

18. See fig. 5, Pl. III. This is made upon the alt-azimuth system, and the plates are marked according to the latitude. The circles, called in Latin circuli progressionum, in Arabic Almucantarāt, are circles of altitude, the largest imperfect one representing the horizon (horizon obliquus), and the central dot being the zenith, or pole of the horizon. In my figure, they are compounded by' 5 and 5, but Chaucer's shewed every second degree, i. e. it possessed 45 such circles. For the method of drawing them, see Stöffler, leaf 5, back.

verrey pool of the orisonte in every regioun. And for the more declaracioun, lo here thy figure.

19. From this senith, as it semeth, ther come a maner crokede strykes lyke to the clawes of a loppe, or elles like to the werk of a womanes calle, in kerving overthwart the Almikanteras. And thise same strykes or divisiouns ben cleped Azimuthz. And they devyden the orisonte of thyn Astrolabie in four and twenty 5 devisiouns. And thise Azimutz serven to knowe the costes of the firmament, and to othre conclusiouns, as for to knowe the cenith of the sonne and of every sterre. And for more declaracioun, lo here thy figure.

20. Next thise azimutz, under the Cercle of Cancer, ben ther twelve devisiouns embelif, moche like to the shap of the azimutes, that shewen the spaces of the houres of planetes; and for more declaracioun, lo here thy figure.

21. The Riet of thyn Astrolabie with thy zodiak, shapen in maner of a net or of a loppe-webbe after the olde descripcioun, which thow mayst tornen up and doun as thy-self lyketh, conteneth certein nombre of sterres fixes, with hir longitudes and latitudes determinat; yif so be that the makere have nat erred. The names 5 of the sterres ben writen in the margin of the riet ther as they sitte; of whiche sterres the smale poynt is cleped the Centre. And understond also that alle sterres sittinge with-in the zodiak of thyn Astrolabie ben cleped 'sterres of the north,' for they arysen by northe the est lyne. And alle the remenant fixed, out of the 10 zodiak, ben cleped 'sterres of the south;' but I sey nat that they

19. Some Astrolabes shew 18 of these azimuthal circles, as in my figure (fig. 5, Pl. III). See Stöffler, leaf 13, where will be found also the rules for drawing them.

20. If accurately drawn, these embelife or oblique lines should divide the portions of the three circles below the horizon obliquus into twelve equal parts. Thus each arc is determined by having to pass through three known points. They are called arcus horarum inequalium, as they shew the 'houres inequales.'

21. In fig. 2, Pl. II, the Rete is shewn as it appears when dropped into the depression in the front of the instrument. The shape of it varied much, and another drawing of one (copied from Camb. Univ. MS. Ii. 3. 3, fol. 66 b) is given in fig. 9, Pl. IV. The positions of the stars are marked by the extreme points of the metal tongues. Fig. 2 is taken from the figures in the Cambridge MSS., but the positions of the stars have been corrected by the list of latitudes and longitudes

arysen alle by southe the est lyne; witnesse on Aldeberan and Algomeysa. Generally understond this rewle, that thilke sterres that ben cleped sterres of the north arysen rather than the degree 15 of hir longitude, and alle the sterres of the south arysen after the degree of hir longitude; this is to seyn, sterres fixed in thyn Astrolabie. The mesure of this longitude of sterres is taken in the lyne ecliptik of hevene, under which lyne, whan that the sonne and the mone ben lyne-right or elles in the superfice of this lyne, 20 than is the eclips of the sonne or of the mone; as I shal declare,

and eek the cause why. But sothly the Ecliptik Lyne of thy zodiak is the outtereste bordure of thy zodiak, ther the degrees ben marked.

Thy Zodiak of thyn Astrolabie is shapen as a compas which that 25 conteneth a large brede, as after the quantite of thyn Astrolabie ; in ensample that the zodiak in hevene is imagened to ben a superfice contening a latitude of twelve degrees, wheras al the remenant of cercles in the hevene ben imagined verrey lynes with-oute eny latitude. Amiddes this celestial zodiak ys imagined a lyne, which 30 that is cleped the Ecliptik Lyne, under which lyne is evermo the wey of the sonne. Thus ben ther six degrees of the zodiak on that on side of the lyne, and six degrees on that other. This zodiak is devided in twelve principal devisiouns, that departen the twelve signes. And, for the streitnes of thin Astrolabie, than is 35 every smal devisioun in a signe departid by two degrees and two ; I mene degrees contening sixty minutes. And this forseide hevenissh zodiak is cleped the Cercle of the Signes, or the Cercle of the Bestes; for zodia in langage of Greek sowneth 'bestes' in Latin tonge; and in the zodiak ben the twelve signes that han 40 names of bestes; or elles, for whan the sonne entreth in any of the signes, he taketh the propretee of swich bestes; or elles, for that the sterres that ben there fixed ben disposed in signes of bestes, or shape like bestes; or elles, whan the planetes ben under thilke

given by Stöffler, whom I have followed, not because he is correct, but because he probably represents their positions as they were supposed to be in Chaucer's time very nearly indeed. There was not room to inscribe the names of all the stars on the Rete, and to have written them on the plate below would have conveyed a false impression. A list of the stars marked in fig. 2 is given in the note to § 21, 1. 4. The Ecliptic is the circle which crosses the Equinoctial at its East and West points (fig. 2). In Chaucer's description of the zodiac,

signes, they causen us by hir influence operaciouns and effectes lyk to the operaciouns of bestes. And understonde also, that whan 45 an hot planete cometh in-to an hot signe, than encresseth his hete; and yif a planete be cold, thanne amenuseth his coldnesse, by-cause of the hote signe. And by this conclusioun maystow take ensample in alle the signes, be they moist or drye, or moeble or fix; rekening the qualitee of the planete as I first seide. And everich of 50 thise twelve signes hath respecte to a certein parcelle of the body of a man and hath it in governance; as Aries hath thyn heved, and Taurus thy nekke and thy throte, Gemini thyn armholes and thyn armes, and so forth; as shal be shewed more pleyn in the fifte partie of this tretis. This zodiak, which that is part of the eighte 55 spere, over-kerveth the equinoxial; and he over-kerveth him again in evene parties; and that on half declineth southward, and that other northward, as pleynly declareth the tretis of the spere. And for more declaracioun, lo here thy figure.

22. Thanne hastow a label, that is schapen lyk a rewle, save that it is streit and hath no plates on either ende with holes; but, with the smale point of the forseide label, shaltow calcule thyne equaciouns in the bordure of thin Astrolabie, as by thyn almury. And for the more declaracioun, lo here thy figure.

23. Thyn Almury is cleped the Denticle of Capricorne, or elles the Calculer. This same Almury sit fix in the hed of Capricorne,

5

carefully note the distinction between the Zodiac of the Astrolabe and the Zodiac of Heaven. The former is only six degrees broad, and shews only the northern half of the heavenly zodiac, the breadth of which is imagined to be 12 degrees. Chaucer's zodiac only shewed every other degree in the divisions round its border. This border is divided by help of a table of right ascensions of the various degrees of the ecliptic, which is by no means easily done. See Note on 1. 4 of this section. I may add that the Rete is also called Aranea or Volvellum; in Arabic, Aľancabūt (the spider).

22. The Label. See fig. 6, Pl. III. The label is more usually used on the front of the instrument, where the Rete and other plates revolve. The rule is used on the back, for taking altitudes by help of the scale.

23. The Almury; called also denticulus, ostensor, or 'calculer.' In fig. 2, it may be seen that the edge of the Rete is cut away near the head of Capricorn, leaving only a small pointed projecting tongue, which is the almury or denticle, or (as we should now say) pointer. As the Rete revolves, it points to the different degrees of the border. See also fig. 9, where the almury is plainly marked.