The country was at first divided into nomes.[799] The Thebaïs contained ten, the Delta ten, and the intermediate tract sixteen. But according to some writers, all the nomes together amounted to the number of chambers in the Labyrinth. Now these were less than thirty [six]. The nomes were again divided into other sections. The greater number of the nomes were distributed into toparchies, and these again into other sections; the smallest portions were the arouræ. An exact and minute division of the country was required by the frequent confusion of boundaries occasioned at the time of the rise of the Nile, which takes away, adds, and alters the various shapes of the bounds, and obliterates other marks by which the property of one person is distinguished [CAS. 787] from that of another. It was consequently necessary to measure the land repeatedly. Hence it is said geometry originated here, as the art of keeping accounts and arithmetic originated with the Phœnicians, in consequence of their commerce.[800] As the whole population of the country, so the separate population in each nome, was divided into three classes; the territory also was divided into three equal portions. The attention and care bestowed upon the Nile is so great to cause industry to triumph over nature. The ground by nature, and still more by being supplied with water, produces a great abundance of fruits. By nature also a greater rise of the river irrigates a larger tract of land; but industry has completely succeeded in rectifying the deficiency of nature, so that in seasons when the rise of the river has been less than usual, as large a portion of the country is irrigated by means of canals and embankments, as in seasons when the rise of the river has been greater. Before the times of Petronius there was the greatest plenty, and the rise of the river was the greatest when it rose to the height of fourteen cubits; but when it rose to eight only, a famine ensued. During the government of Petronius, however, when the Nile rose twelve cubits only, there was a most abundant crop; and once when it mounted to eight only, no famine followed. Such then is the nature of this provision for the physical state of the country. We shall now proceed to the next particulars. 4. The Nile, when it leaves the boundaries of Ethiopia, flows in a straight line towards the north, to the tract called the Delta, then “cloven at the head,” (according to the expression of Plato,) makes this point the vertex, as it were, of a triangle, the sides of which are formed by the streams, which separate on each side, and extend to the sea, one on the right hand to Pelusium, the other on the left to Canobus and the neighbouring Heracleium, as it is called; the base is the coast lying between Pelusium and the Heracleium.