Of these sanctuaries the most venerable was that of Bel the Elder at Nippur. It has been systematically excavated by the Americans down to its foundations, and the successive strata of its history laid bare. Inscribed objects have been found in all the strata, carrying the history of the cuneiform system of writing back to the days when the temple was originally built. But it is still the cuneiform system of writing as far back as we can go, that is to say the characters are the cursive forms of earlier hieroglyphic pictures, the features of which are in most cases scarcely traceable. Here and there, it is true, the primitive pictorial form has been preserved, but this is the exception and not the rule. As a rule the earliest writing found at Nippur, and coeval with the foundation of its temple, is already the degenerated and cursive hand which we call cuneiform. The fact is very noteworthy. The cuneiform characters have assumed the shapes which give them their name owing to their having been inscribed on clay by a stylus of wood or metal, which obliged the writer to substitute a series of wedge-like indentations for curves and straight lines. As time went on, the number of the wedges was reduced, the forms of the characters were simplified, and the resemblance to the pictures they were once intended to represent became more and more indistinct. The cuneiform script is, in short, a running hand, like the hieratic of Egypt. But whereas in Egypt the hieratic running hand does not come into common use until long after the beginning of the monumental period, while the pictorial hieroglyphs continued to be employed to the last, in Babylonia the cuneiform running hand has superseded the primeval pictures as far back as our records carry us. When the temple of Nippur was built--and it was probably one of the first, if not the first, to be built in the Babylonian plain--the clay tablet was already in use for writing purposes, and the cursive cuneiform had taken the place of the older hieroglyphs. The Babylonian plain was called by its Sumerian inhabitants the Edin, or “Plain,” a name which was borrowed by the Semites and has been made familiar to us by the book of Genesis. Originally it had meant all the uncultivated flats on either side of the Euphrates, but it soon acquired the sense of the country as opposed to the city, and so of the cultivated plain itself. Most of the important Babylonian cities were built in it between the Euphrates on the west and the Tigris on the east. A few only lay beyond it on the western bank of the Euphrates. One of these was Eridu, another was Ur, a third was Borsippa. [Illustration: THE TELL OF BORSIPPA, THE PRESENT BIRS-NIMRUD.]