Similar remarks would apply to observations of the moon, which could also be directly observed. The planets and stars of course could only be observed directly.
The grand gallery could be used for the observation of any celestial body southing higher than 26° 18' above the horizon; but not very effectively for objects passing near the zenith. The Pleiades could be well observed. They southed about 63-2/3° above the horizon in the year 2140 B.C. or thereabouts when they were on the equinoctial colure.[46] But if I am right in taking the year 3300 B.C. when Alpha Centauri shone down the smaller ascending passage in southing, the Pleiades were about 58° only above the horizon when southing, and therefore even more favourably observable from the great meridional gallery.
In passing I may note that at this time, about 3300 years before our era, the equinoctial point (that is, the point where the sun passes north of the equator, and the year begins according to the old manner of reckoning) was midway between the horns of the Bull. So that then, and then alone, a poet might truly speak of spring as the time
"Candidus auratis aperit quum cornibus annum Taurus."
as Virgil incorrectly did (repeating doubtless some old tradition) at a later time. Even Professor Smyth notices the necessity that the pyramid gallery should correspond in some degree with such a date. "For," says he, "there have been traditions for long, whence arising I know not, that the seven overlappings of the grand gallery, so impressively described by Professor Greaves, had something to do with the Pleiades, those proverbially seven stars of the primeval world," only that he considers the pyramid related to _memorial_ not _observing_ astronomy, "of an earlier date than Virgil's." The Pleiades also, it may be remarked, were scarcely regarded in old times as belonging to the constellation of the Bull, but formed a separate asterism.
The upper end of the great gallery lies very near the vertical axis of the pyramid. It is equidistant, in fact, from the north and south edges of the pyramid platform at this level, but lies somewhat to the east of the true centre of this platform. One can recognise a certain convenience in this arrangement, for the actual centre of the platform would be required as a position from whence observation of the whole sky could be made. Observers stationed there would have the cardinal points and the points midway between them defined by the edges and angles of the square platform, which would not be the case if they were displaced from the centre. Stationed as they would be close to the mouth of the gallery, they would hear the time signallings given forth by the observers placed at various parts of the gallery; and no doubt one chief end of the exact time-observations for which the gallery was manifestly constructed, would be to enable the platform observers duly to record the time when various phenomena were noticed in any part of the heavens.