31. The varying length of days and the di¡erent position of the shadows
TRANSLATION
Hence it is necessary, in order to preserve the rule of truth, that we state clearly both that the Pasch is not to be sacri¢ced before the equinox and before the darkness has been overcome, and that this equinox is rightfully to be assigned to the 12th kalends of April [March
21], as we are instructed not only by the authority of the Fathers, but also by examining the sundial [horologica consideratione]. /376/ But the other three termini of the seasons are, by an analogous reasoning, to be observed the same number of days before the 8th kalends of the following
[month].
31. THE VARYING LENGTH OF DAYS AND THE
DIFFERENT POSITION OF THE SHADOWS
While the equinox falls on the same day, and that day is of the same length, everywhere in the world, the solstice and all the other days are of di¡erent lengths because of disparate climates, and the [disparate] shadows [cast by the Sun]. The books composed through the e¡orts of both gentiles and Christians, and competent observers hailing from both regions (that is, north and south) show this plainly. For St Ambrose, discussing the seasons and the path of the Sun in the fourth book of his Hexaemeron, says, amongst other things: A shadow is less at midday than it is either at the beginning of the day or at the end, and this is true where we live, in the west. There are those in southern climes who have no shadow at noon on two days of the year; having the Sun directly overhead, they are illuminated all around on every side. Hence they are called ''shadowless'' [ascii] from the Greek [a' a¤skioB]. Many claim that the Sun is so high in the sky that through the narrow mouth of a well, they can see the water glinting in the depths. In the south there are said to be people called ''am¢scii''275 [''shadowed all about''] because they cast a shadow on both sides.276 And a little later: In this part of the world in which we live, there are people dwelling in the south who seem to cast a shadow towards the south. This is said to happen in high summer, when the Sun travels towards the north.277 Basil himself writes things which are similar to this in his commentary on Genesis.
But /377/ Pliny also, in a book which is non-religious, yet not to be 275 From the Greek a'mfis¤ skioB.
276 Ambrose, Hexaemeron 4.5.23 (130.11^20).
277 Ibid. (131.4^7).
THE RECKONING OF TIME
condemned,expoundingthesemattersatgreaterlength,writesasfollows:
Sundials cannot be used everywhere because the Sun's shadows change every 300, or at most 500 stadia. Hence in Egypt at noon on the equinox, the shadow of the pin, which they call the gnomon, is a little more than half the length of the gnomon. In the city of Rome the shadow is 1
19 shorter than the gnomon, in the town of Ancona it is longer by
35, and in the region of Italy they call Venetia the shadow at the same hour is equal to the gnomon. Likewise they report that in the town of Syene, which is 5,000 stadiaupstreamfromAlexandria,noshadowiscastatnoononthesolstice, and that a well, constructed for the sake of this experiment, is illuminated from topto bottom. From this it would appearthatthe Sun is straight overhead in that region, and Onesicretus writes that this occurs at the same time in India abovethe river Hypasis.They say that in Berenice, thecity of the Trogodytes, and 4,820 stadia away in the same region in the town of Ptolomais,whichwasbuiltontheshoresoftheRedSeaforthe¢rstelephant hunts, this same thing occurs forty-¢ve days before the solstice, /378/ and forty-¢ve days after, and after those ninety days the shadows fall to the south. Again, in Meroe, an inhabited island in the Nile River and the capital of the Ethiopian people 5,000 stadia from Syene, the shadows disappear twice each year, when the Sun reaches the eighteenth degree of Taurus and fourteenth of Leo. In the midst of the Indian tribe of the Oretes there is a mountain called Maleus; near it, the shadows in summer fall to the south and those in the winter to the north; the north [celestial pole] appears there on only 15 nights. In the famous port of Patalia in India, the sun rises on the right and the shadows fall to the south. When Alexander stayed there, it was noticed that the north [celestial pole] could be seen only during the ¢rst part of the night. His guide Onesicretus wrote that in those parts of India where there are no shadows, the north [celestial pole] cannot be seen, and therefore these parts are called shadowless, and the hours are not reckoned there. And Eratosthenes relatesthat overthe whole land of the Trogodytes the shadows fall in the wrong direction for 90 days out of the year. Thus it happens that, due to variation in the increment of daylight, the longest day in Meroe measures twelve equinoctial hours and eight parts of an hour, but in Alexandria fourteen hours, in Italy ¢fteen, and in Britain seventeen, where the bright nights of summer con¢rm what reason compels us to believe: /379/that when the Sun is climbing closer to the topmost point of the world during the [summer] solstice, the lands which lie beneath [the Pole], because of the narrow circuit of light, have continuous day for six months, and then [continuous] night, when [the