But it is to the Egyptian successors of Alexander that we must look for the systematic extension of commerce; towards which they were in a manner impelled by the highly favourable situation of Alexandria. It has justly been observed by Harris, in his Collection of Voyages, that most of the cities founded by the Syrian kings existed little longer than their founders; and, perhaps, with the exception of Antioch, on the Orontes, and Seleucia, on the Tigris, none of them, from the situation in which they were built, and the countries by which they were surrounded, could under any circumstances be of long duration. With respect to the cities founded by Alexander it was quite otherwise. The Alexandria of Paropamisus may still be traced in Candahar; and the Alexandria on the Iaxartes, in Cogend: and the Alexandria of Egypt, after surviving the revolutions of empires for eighteen ages, perished at last, (as a commercial city,) only in consequence of a discovery which changed the whole system of commerce through the world. On the destruction of Tyre, Alexander sought for a situation on which he might build a city that would rival it in the extent of its commerce; and he quickly perceived the advantages that would be derived from the seat of commerce being established near one of the branches of the Nile. By means of this river his projected city would command at once the commerce of the Red Sea and the Mediterranean. It was, however, necessary to select a spot near the mouths of the Nile, which would secure these advantages in the highest degree, and which would at the same time be of the highest importance in a military point of view, and afford a harbour constantly accessible. The site of Alexandria combined all these advantages: on three sides it has the sea, or the lake Mareotis, which, according to Strabo, was nearly 300 stadia long, and 150 broad; the country adjoining this lake was fertile, and by means of it, and natural or artificial channels, there was a communication with the Delta and Upper Egypt. Between this lake and the Canopic branch of the Nile, Alexander built his city: to less sagacious minds this site would have appeared improper and injudicious in some respects; for the sea-coast from Pelusium to Canopus is low land, not visible at a distance; the navigation along this coast, and the approach to it, is dangerous, and the entrance into the mouths of the Nile, at some seasons, is extremely hazardous. But these disadvantages the genius of Alexander turned to the benefit of his city, by the erection of the Pharos, and the plan of a double harbour, which was afterwards completed by the Ptolemies; for he thus united in a single spot the means of defence and facility of access.