These variations are comparatively trifling. There are more important ones arising from other causes. As the river-bed rises, the banks also rise. This is brought about by the more luxuriant vegetation and the activity of the husbandmen in the neighbourhood of the banks, as well as by an occasional overflow, when naturally the largest share of sediment is deposited near the river. Thus the river flows over what may be termed an artificially raised bed between two raised banks; the surface of the water is actually higher than the plain beyond the banks, a difference which the unaided eye can scarcely detect as it deals with a rise of only a few metres over an extent of several hundred. At a specially high flood, however, or owing to carelessness in dealing with the canals, the river bursts its banks, rushes out over the lower plain, and, unhindered by any obstacles, makes its way lower down into its ancient bed. This happened in modern times in Musseyib, when the Euphrates left its ancient bed, from Musseyib to Samaua, and transferred itself to the western Hindiyeh branch. It appears to have flowed appreciably more to the west in the neighbourhood of Divaniyeh in ancient times. According to a plan of the city found on the spot, Nippur seems to have lain on the Euphrates. Fara also, the ancient Shuruppak, where the Babylonian Noah built his ark, and which we have excavated, is represented on the border of the river, though it now lies 12 hours from Divaniyeh. These great shiftings of the river must have altered the geographical and topographical aspect of the country to an extraordinary degree in the course of hundreds and thousands of years. When we attempt to discover the reason for selecting a particular site for an ancient town we are confronted by the difficulty of not knowing where the ancient canals lay. The ruined canals of to-day go back, perhaps without exception, to the Middle Ages of Arab rule. The great “Habl Ibrahim” is on the whole no older than this. Whether an ancient canal of similar extent ran in its immediate neighbourhood we do not know; there are no remains of one. Certain ancient watercourses, as those at Nippur or Fara, can no longer be recognised on the surface. The river bank at Fara was first brought to light by excavation.