PAVO, the Peacock, lies north of Octans and Apus, and south of Telescopium. Its brightest star is α, which is a fine bright star (2·12 Harvard). κ is a short-period variable. It varies from 3·8 to 5·2, and the period is about 9 days. This is an interesting object, as all the fluctations of light can be observed by the naked eye or an opera-glass. ε Pavonis was measured 4·10 at Harvard, but the Cordoba estimates vary from 3·6 to 4·2. Gould says "it is of a remarkably blue colour." INDUS.--This constellation lies north of Octans, and south of Sagittarius, Microscopium, and Grus. One of its stars, α, is probably referred to by Al-Sufi in his description of Sagittarius; it lies nearly midway between β Sagittarii and α Gruis, and is the brightest star of the constellation. The star ε Indi (4·74 Harvard) has a remarkably large proper motion of 4"·68 per annum. Its parallax is about 0"·28, and the proper motion indicates a velocity of about 49 miles a second at right angles to the line of sight. TOUCAN.--This constellation lies north of Octans, and south of Phœnix and Grus, east of Indus, and west of Hydrus. Its brightest star is α, of about the 3rd magnitude. * * * * * There are seven "celestial rivers" alluded to by the ancient astronomers:-- 1. The Fish River, which flows from the urn of Aquarius. 2. The "River of the Bird," or the Milky Way in Cygnus. 3. The River of the Birds--2, including Aquila. 4. The River of Orion--Eridanus. 5. The River of the god Marduk--perhaps the Milky Way in Perseus. 6. The River of Serpents (Serpens, or Hydra). 7. The River of Gan-gal (The High Cloud)--probably the Milky Way as a whole. There are four serpents represented among the constellations. These are Hydra, Hydrus, Serpens, and Draco. According to the late Mr. Proctor the date of the building of the Great Pyramid was about 3400 B.C.[452] At this time the Spring Equinox was in Taurus, and this is referred to by Virgil. But this was not so in Virgil's time, when--on account of the precession of the equinoxes--the equinoctial point had already entered Pisces, in which constellation it still remains. At the date 3400 B.C. the celestial equator ran along the whole length of the constellation Hydra, nearly through Procyon, and a little north of the bright red star Antares. The star Fomalhaut (α Piscis Australis) is interesting as being the most southern 1st magnitude star visible in England, its meridian altitude at Greenwich being little more than eight degrees.[453]