There is another building, too, that is highly celebrated; the tower that was built by a king of Egypt, on the island of Pharos, at the entrance to the [1] harbour of Alexandria. The cost of its erection was eight hundred talents, they say; and, not to omit the magnanimity that was shown by King Ptolemæus[2] on this occasion, he gave permission to the architect, Sostratus[3] of Cnidos, to inscribe his name upon the edifice itself. The object of it is, by the light of its fires at night, to give warning to ships, of the neighbouring shoals, and to point out to them the entrance of the harbour. At the present day, there are similar fires lighted up in numerous places, Ostia and Ravenna, for example. The only danger[4] is, that when these fires are thus kept burning without intermission, they may be mistaken for stars, the flames having very much that appearance at a distance. This architect 'is the first person that built a promenade upon arches; at Cnidos, it is said.