The more ancient of these sites are in the southern portion of the country, in that region anciently known as Sumir, or Shinar, and later as Chaldea. This was on the lower courses of the great rivers, the Tigris and Euphrates, towards the Persian Gulf. This region abounds with the ruins of ancient cities as yet unexplored. The most important of the cities of this region were Eridu, the most ancient and sacred, now marked by the mud heaps of Abu Sharein; the city of Ur, now Mugheir, once a maritime and commercial city of these earlier times, and of special interest as that “Ur of the Chaldees,” the early home of Abraham; Nippur, or Neffur, the seat of older Bel; Tel-Loh, the ancient Sirgulla, and Larsa. The sites of Ur and Eridu, once near the sea, are now far inland. Eridu, formerly directly upon the shores of the Persian Gulf, is now one hundred and fifty miles distant, while Ur, once situated at the mouth of the Euphrates, is now about one hundred and fifty miles distant from the sea, and about six miles to the west of the present course of the Euphrates on the western banks of the older bed of the river, nearly opposite the point—though six miles away—where the Shat-el-Hic enters the Euphrates from the east, as it approaches from its source in the Tigris. It is estimated that the alluvium brought down by these great rivers has encroached upon the Persian Gulf by the formation of land about sixty feet annually, creating a delta at the head of the gulf of ninety miles in three thousand years. These deposits have been more rapid in later times than anciently. The great cause of the difference between ancient and modern Chaldea is the neglect of the water courses. In ancient times, a well arranged system of embankments and irrigating canals held these great rivers in their courses by distributing the superabundant waters of the great flood times to all parts of the country, thus enriching the soil with abundant water supply at all seasons. In the present neglected condition of this region the floods as they come down from the mountain sources of the Euphrates are liable to wash away the banks, sometimes changing the course of the river, and overflowing large tracts at slightly lower levels, which have become unwholesome marshes, while other large tracts which are never inundated, in the fierce heats become parched and desolate sand wastes. It is said that such is the spread and waste of the Euphrates in its lower course, that, except in flood time, but a small proportion of this great volume of water reaches the sea. These conditions do not so seriously affect the Tigris, which for the greater part of its course flows over a rocky bed, between high embankments, and which, though a narrower, is a deeper and swifter stream than the Euphrates.