From what people the Greeks received the celestial sphere, is a question on which more than one opinion has been formed. One is that it was originated in the tropical latitudes of Egypt. The other, that it came from the Chaldeans, and a third that it came from more temperate latitudes further to the east. The arguments for the last of these are as follow:
There is an empty space of about 90°, formed by the last constellations of the sphere, towards the south pole, that is by the Centaur, the Altar, the Archer, the Southern Fish, the Whale, and the Ship. Now in a systematic plan, if the author were situated near the equator there would be no vacant space left in this way, for in this case the southern stars, attracting as much attention as the northern, would be inevitably inserted in the system of constellations which would be extended to the horizon on all sides. But a country of sufficiently high latitude to be unable to see at any time the stars about the southern pole must be north both of Egypt and Chaldea.
This empty space remained unfilled until the discovery of the Cape of Good Hope, except that the star Canopus was included in the constellation Argo, and the river Eridan had an arbitrary extension given to it, instead of terminating in latitude 40°.
Another less cogent argument is derived from the interpretation of the fable of the Phœnix. This is supposed to represent the course of the sun, which commences its growth at the time of its death. A similar fable is found among the Swedes. Now a tropical nation would find the difference of days too little to lead it to invent such a fable to represent it. It must needs have arisen where the days of winter were very much shorter than those of summer.
The Book of Zoroaster, in which some of the earliest notices of astronomy are recorded, states that the length of a summer day is twice as long as that of winter. This fixes the latitude in which that book must have been composed, and makes it 49°. Whence it follows, that to such a place must we look for the origin of these spheres, and not to Egypt or Chaldea.
Plate III.—Chaldean Astronomers.
Diodorus Siculus speaks of a nation in that part of the world, whom he calls Hyperboreans, who had a tradition that their country is the nearest to the moon, on which they discovered mountains like those on the earth, and that Apollo comes there once every nineteen years. This period being that of the metonic cycle of the moon, shows that if this could have really been discovered by them, they must have had a long acquaintance with astronomy.
The Babylonian tablets lead us to the belief that astronomy, and with it the sphere, and the zodiac were introduced by a nation coming from the East, from the mountains of Elam, called the Accadians, before 3000 B.C., and these may have been the nation to whom the whole is due.