In ancient Egypt Orion was called _Sahu_. This name occurs on the monuments of the Ptolemies, and also on those of the Pharaohs. It is also mentioned in the _Book of the Dead_. It seems to have been considered of great importance in ancient Egypt, as its heliacal rising announced that of Sirius, which heralded the annual rising of the Nile. The constellation Eridanus lies south of Taurus, east of Cetus, and west of Lepus. In ancient times it was supposed to represent the Nile or the Po. Ptolemy merely calls it Ποταμου αστερισμος, or asterism of the river. It was called Eridanus by the Greeks, and Fluvius by the Romans. It appears to correspond with the Hebrew Shicor. Al-Sufi calls it _al-nahr_, "the River." One of the most interesting points in Al-Sufi's most interesting work is the identity of the bright star known to the ancient astronomers as _achir al-nahr_, "the End of the River," and called by Ptolemy Εσχατος του ποταμου, "the Last in the River." Some astronomers have identified this star with α Eridani (Achernar), a bright southern star of the 1st magnitude, south of Eridanus. But Al-Sufi's description shows clearly that the star he refers to is really θ Eridani; and the reader will find it interesting to follow his description with a star map before him. Describing Ptolemy's 34th star of Eridanus (the star in question), he says, "the 34th star is found before [that is west of] these three stars [the 31st, 32nd, and 33rd, which are υ{2}, Du, and υ' in Proctor's Atlas], the distance between it and that of the three which is nearest being about 4 cubits [9° 20']. It is of the first magnitude; it is that which is marked on the southern astrolabe, and called _achir al-nahr_, 'the End of the River.' There are before this bright one two stars, one to the south, [σ Eridani, not shown in Proctor's small Atlas], the other to the north [ι Eridani]; Ptolemy does not mention these. One of these stars is of the 4th magnitude, the other of the 5th. There is behind the same [that is, east of it] a star of the 4th magnitude distant from it two cubits [ε Eridani]. To the south of the three stars which follow the bright one there are some stars of the 4th and 5th magnitudes, which he [Ptolemy] has not mentioned." Now, a glance at a star map of this region will show clearly that the bright star referred to by Al-Sufi is undoubtedly θ Eridani, which is therefore the star known to the ancients as the "End of the River," or the "Last in the River."