+48.+ The Apasiacae live between the rivers Oxus and Tanais, the former of which falls into the Hyrcanian Sea, the latter into the Palus Maeotis.[15] Both are large enough to be navigable; and it seems surprising how the Nomads managed to come by land into Hyrcania along with their horses. Two accounts are given of this affair, one of them probable, the other very surprising yet not impossible. The Oxus rises in the Caucasus, and being much augmented by tributaries in Bactria, it rushes through the level plain with a violent and turbid stream. When it reaches the desert it dashes its stream against some precipitous rocks with a force raised to such tremendous proportions by the mass of its waters, and the declivity down which it has descended, that it leaps from the rocks to the plain below leaving an interval of more than a stade between the rock and its falls. It is through this space that they say the Apasiacae went on foot with their horses into Hyrcania, under the fall, and keeping close to the rock. The other account is more probable on the face of it. It is said that, as the basin of the river has extensive flats into which it descends with violence, the force of the stream makes hollows in them, and opens chasms into which the water descends deep below the surface, and so is carried on for a short way, and then reappears: and that the barbarians, being well acquainted with the facts, make their way on horseback, over the space thus left dry, into Hyrcania.... [Sidenote: Battle on the river Arius between Antiochus and the Bactrians.]