The course of the Nile from Elephantine, where it entered Egypt, to Cercasorus, near Heliopolis, where it bifurcated, was in general north, with, however, a certain tendency westward. It entered Egypt nearly in long. 33°, and at Neapolis (more than two degrees further north) it was still within 15° of the same meridian; then, however, it took a westerly bend, crossed the 32nd and 31st meridians, and in lat. 28° 23 reached west as far as long. 30° 43’. After this it returned a little eastward, recrossed the 31st meridian, and having reached long. 31° 22’ near Aphroditopolis (lat.29° 25), it proceeded almost due north to Cercasorus in lat. 30° 7’. The course of the river up to this point was, from its entry into the country, about 540 miles. At Cercasorus the Delta began. The river threw out two branches, which flowed respectively to the north-east and the north-west, while between them was a third channel, a continuation of the previous course of the stream, which pierced the Delta through its centre, flowing almost due north. Lower down, further branch channels were thrown out, some natural, some artificial, and the triangular tract between the two outer arms of the river was intersected by at least five, and (in later times) by fourteen large streams. The right and left arms appear to have been of about equal in length, and may be estimated at 150 or 160 miles; the central arm had a shorter course, not exceeding 110 miles. The volume of water which the Nile pours into the Mediterranean during a day and night is estimated at from 150,000 millions to 700,000 millions of cubic metres. It was by far the largest of all the rivers of the Empire.