“The scenery above Hit, in itself very picturesque, is greatly heightened, as one is carried along the current, by the frequent recurrence, at very short intervals, of ancient irrigating aqueducts; these beautiful specimens of art and durability are attributed by the Arabs to the times of the ignorant, meaning (as is expressly understood) the Persians, when fire-worshippers, and in possession of the world. They literally cover both banks, and prove that the borders of the Euphrates were once thickly inhabited by a people far advanced indeed in the application of hydraulics to domestic purposes, of the first and greatest utility—the transport of water. The greater portion is now more or less in ruins, but some have been repaired, and kept up for use either to grind corn or to irrigate. The aqueducts are of stone, firmly cemented, narrowing to about two feet or twenty inches at top, placed at right angles to the current, and carried various distances towards the interior, from two hundred to one thousand two hundred yards. “But what most concerns the subject of this memoir is, the existence of a parapet wall or stone rampart in the river, just above the several aqueducts. In general, there is one of the former attached to each of the latter. And almost invariably, between two mills on the opposite banks, one of them crosses the stream from side to side, with the exception of a passage left in the centre for boats to pass up and down. The object of these subaqueous walls would appear to be exclusively, to raise the water sufficiently at low seasons, to give it impetus, as well as a more abundant supply to the wheels. And their effect at those times is, to create a fall in every part of the width, save the opening left for commerce, through which the water rushes with a moderately irregular surface. These dams were probably from four to eight feet high originally; but they are now frequently a bank of stones disturbing the evenness of the current, but always affording a sufficient passage for large boats at low seasons.”