The three circles[485], which are connected with the above-mentioned zones, distinguish the inequalities of the seasons; these are, the solstitial circle, which proceeds from the part of the Zodiac the highest to us and approaching the nearest to the district of the north; on the other side, the brumal, which is towards the south pole; and the equinoctial, which traverses the middle of the Zodiac.
CHAP. 71.—OF THE INEQUALITY OF CLIMATES.
The cause of the other things which are worthy of our admiration depends on the figure of the earth itself, which, together with all its waters, is proved, by the same arguments, to be a globe. This certainly is the cause why the stars of the northern portion of the heavens never set to us, and why, on the other hand, those in the south never rise, and again, why the latter can never be seen by the former, the globe of the earth rising up and concealing them. The Northern Wain is never seen in Troglodytice[486], nor in Egypt, which borders on it[487]; nor can we, in Italy, see the star Canopus[488], or Berenice’s Hair[489]; nor what, under the Emperor Augustus, was named Cæsar’s Throne, although they are, there[490], very brilliant stars. The curved form of the earth is so obvious, rising up like a ridge, that Canopus appears to a spectator at Alexandria to rise above the horizon almost the quarter of a sign; the same star at Rhodes appears, as it were, to graze along the earth, while in Pontus it is not seen at all; where the Northern Wain appears considerably elevated. This same constellation cannot be seen at Rhodes, and still less at Alexandria. In Arabia, in the month of November, it is concealed during the first watch of the night, but may be seen during the second[491]; in Meroë it is seen, for a short time, in the evening, at the solstice, and it is visible at day-break, for a few days before the rising of Arcturus[492]. These facts have been principally ascertained by the expeditions of navigators; the sea appearing more elevated or depressed in certain parts[493]; the stars suddenly coming into view, and, as it were, emerging from the water, after having been concealed by the bulging out of the globe[494]. But the heavens do not, as some suppose, rise higher at one pole, otherwise[495] its stars would be seen from all parts of the world; they indeed are supposed to be higher by those who are nearest to them, but the stars are sunk below the horizon to those who are more remote. As this pole appears to be elevated to those who are beneath it; so, when we have passed along the convexity of the earth, those stars rise up, which appear elevated to the inhabitants of those other districts; all this, however, could not happen unless the earth had the shape of a globe.
CHAP. 72.—IN WHAT PLACES ECLIPSES ARE INVISIBLE, AND WHY THIS IS THE CASE.
Hence it is that the inhabitants of the east do not see those eclipses of the sun or of the moon which occur in the evening, nor the inhabitants of the west those in the morning, while such as take place at noon are more frequently visible[496]. We are told, that at the time of the famous victory of Alexander the Great, at Arbela[497], the moon was eclipsed at the second hour of the night, while, in Sicily, the moon was rising at the same hour. The eclipse of the sun which occurred the day before the calends of May, in the consulship of Vipstanus and Fonteius[498], not many years ago, was seen in Campania between the seventh and eighth hour of the day; the general Corbulo informs us, that it was seen in Armenia, between the eleventh and twelfth hour[499]; thus the curve of the globe both reveals and conceals different objects from the inhabitants of its different parts. If the earth had been flat, everything would have been seen at the same time, from every part of it, and the nights would not have been unequal; while the equal intervals of twelve hours, which are now observed only in the middle of the earth, would in that case have been the same everywhere.
CHAP. 73. (71.)—WHAT REGULATES THE DAYLIGHT ON THE EARTH.
Hence it is that there is not any one night and day the same, in all parts of the earth, at the same time; the intervention of the globe producing night, and its turning round producing day[500]. This is known by various observations. In Africa and in Spain it is made evident by the Towers of Hannibal[501], and in Asia by the beacons, which, in consequence of their dread of pirates, the people erected for their protection; for it has been frequently observed, that the signals, which were lighted at the sixth hour of the day, were seen at the third hour of the night by those who were the most remote[502]. Philonides, a courier of the above-mentioned Alexander, went from Sicyon to Elis, a distance of 1200 stadia, in nine hours, while he seldom returned until the third hour of the night, although the road was down-hill[503]. The reason is, that, in going, he followed the course of the sun, while on his return, in the opposite direction, he met the sun and left it behind him. For the same reason it is, that those who sail to the west, even on the shortest day, compensate for the difficulty of sailing in the night and go farther[504], because they sail in the same direction with the sun.
CHAP. 74. (72.)—REMARKS ON DIALS, AS CONNECTED WITH THIS SUBJECT.
The same dial-plates[505] cannot be used in all places, the shadow of the sun being sensibly different at distances of 300, or at most of 500 stadia[506]. Hence the shadow of the dial-pin, which is termed the gnomon, at noon and at the summer solstice, in Egypt, is a little more than half the length of the gnomon itself. At the city of Rome it is only 1⁄9 less than the gnomon, at Ancona not more than 1⁄35 less, while in the part of Italy which is called Venetia, at the same hour, the shadow is equal to the length of the gnomon[507].