Thus it appears that Chaucer's method of determining the date was incorrect but his calculations in observing the sun's position were quite accurate. For fuller particulars see Chaucer's _Astrolabe_, ed. Skeat (E. E. T. S.) preface, p. 1. III. It was customary in ancient times and even as late as Chaucer's century to determine the position of the sun, moon, or planets at any time by reference to the signs of the zodiac. The _zodiac_ is an imaginary belt of the celestial sphere, extending 8° on each side of the ecliptic, within which the orbits of the sun, moon, and planets appear to lie. The zodiac is divided into twelve equal geometric divisions 30° in extent called _signs_ to each of which a fanciful name is given. The signs were once identical with twelve constellations along the zodiac to which these fanciful names were first applied. Since the signs are purely geometric divisions and are counted from the spring equinox in the direction of the sun's progress through them, and since through the precession of the equinoxes the whole series of signs shifts westward about one degree in seventy-two years, the signs and constellations no longer coincide. Beginning with the sign in which the vernal equinox lies the names of the zodiacal signs are Aries (Ram), Taurus (Bull), Gemini (Twins), Cancer (Crab), Leo (Lion), Virgo (Virgin), Libra (Scales), Scorpio (Scorpion), Sagittarius (Archer), Aquarius (Water-carrier), and Pisces (Fishes). In this passage, the line "That in the Ram is four degrees up-ronne" indicates the date March 16. This can be seen by reference to Figure 1 in Skeat's edition of Chaucer's _Astrolabe_ (E. E. T. S.) The astrolabe was an instrument for making observations of the heavenly bodies and calculating time from these observations. The most important part of the kind of astrolabe described by Chaucer was a rather heavy circular plate of metal from four to seven inches in diameter, which could be suspended from the thumb by a ring attached loosely enough so as to allow the instrument to assume a perpendicular position. One side of this plate was flat and was called the _back_, and it is this part that Figure 1 represents. The back of the astrolabe planisphere contained a series of concentric rings representing in order beginning with the outermost ring: the four quadrants of a circle each divided into ninety degrees; the signs of the zodiac divided into thirty degrees each; the days of the year, the circle being divided, for this purpose, into 365-1/4 equal parts; the names of the months, the number of days in each, and the small divisions which represent each day, which coincide exactly with those representing the days of the year; and lastly the saints' days, with their Sunday-letters. The purpose of the signs of the zodiac is to show the position of the sun in the ecliptic at different times. Therefore, if we find on the figure the fourth degree of Aries and the day of the month