Polybius, The Histories of Polybius, Vol…
“ 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 47stream 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. ”
