Deeper down the strata were irregular. Here they do not lie throughout in one solid uniform line. At 1 metre below zero we came once more on a uniform, clearly marked stratum with houses lying rather closely together, in which were found tablets with dates of the time of the first Babylonian kings, the immediate successors of Hammurabi (2250 B.C.), Samsuiluna, Ammiditana, Samsuditana, etc. The mud-brick walls of the houses are not very thick, but all of them rest on a foundation of burnt brick. They show numerous traces of a conflagration in which they were destroyed. The tablets lay among these undisturbed ashes, so there can be no doubt that they were contemporary (see section on Fig. 237). [Illustration: FIG. 155.—Plan of Merkes. ] This is a bare outline of the find in the north of Merkes. If we dig farther in the plain, we find the Nebuchadnezzar stratum nearer the surface, and the Hammurabi stratum disappears below water-level. This means undoubtedly that as far back as the latter period the town level here was rising in the form of a mound, and that at the Parthian period no substantial buildings stood in the plain. The streets, though not entirely regular, show an obvious attempt to run them as much in straight lines as possible, so that Herodotus (i. 180) was able to describe them as straight (ἰθέαι). They show a tendency to cross at right angles, about 16 degrees west of north, and therefore as many degrees north of east. The Procession Street on the whole follows the same direction, and so do the inner city walls and all the temples, including Esagila, which may perhaps be held mainly responsible for this orientation. Only the Palace buildings on the Kasr and the mound Babil face exactly towards the astronomical north. The lower and more ancient levels also maintain this direction, in general with very slight deviations in the lines of the streets. Too little is known of the Hammurabi period at present to give any general valid rule with certainty; the house walls that have been excavated face somewhat accurately to the north, as do those of the upper levels. It was this fact, in conjunction with the usual inexact rectangular arrangement of the plots of land, and the exact rectangles of the inner chambers that gave rise to the peculiar construction of the street walls, which on their whole length were furnished with projecting corners or steps, an extraordinary characteristic of Neo-Babylonian architecture, which we have already met with at the Southern Citadel (Fig. 156).