The material used by the Babylonians in their constructions seems to have been almost entirely brick.  Like the early Chaldaeans, they employed bricks of two kinds, both the ruder sun-dried sort, and the very superior kiln-baked article.  The former, however, was only applied to platforms, and to the interior of palace mounds and of very thick walls, and was never made by the later people the sole material of a building.  In every case there was at least a revetement of kiln-dried brick, while the grander buildings were wholly constructed of it.  The baked bricks used were of several different qualities, and (within rather narrow limits) of different sizes.  The finest quality of brick was yellow, approaching to our Stourbridge or fire-brick; another very hard kind was blue, approaching to black; the commoner and coarser sorts were pink or red, and these were sometimes, though rarely, but half-baked, in which case they were weak and friable.  The shape was always square; and the dimensions varied between twelve and fourteen inches for the length and breadth, and between three and four inches for the thickness. [PLATE XVII., Fig. 1.] At the corners of buildings, half-bricks were used in the alternate rows, since otherwise the joinings must have been all one exactly over another.  The bricks were always made with a mold, and were commonly stamped on one face with an inscription.  They were, of course, ordinarily laid horizontally.  Sometimes, however, there was a departure from this practice.  Rows of bricks were placed vertically, separated from one another by single horizontal layers.  This arrangement seems to have been regarded as conducing to strength, since it occurs only where there is an evident intention of supporting a weak construction by the use of special architectural expedients.

[Illustration:  PLATE XVII.]

The Babylonian builders made use of three different kinds of cement.  The most indifferent was crude clay, or mud, which was mixed with chopped straw, to give it greater tenacity, and was applied in layers of extraordinary thickness.  This was (it is probable) employed only where it was requisite that the face of the building should have a certain color.  A cement superior to clay, but not of any very high value, unless as a preventive against damp, was bitumen, which was very generally used in basements and in other structures exposed to the action of water.  Mortar, however, or lime cement was far more commonly employed than either of the others, and was of very excellent quality, equal indeed to the best Roman material.

There can be no doubt that the general effect of the more ambitious efforts of the Babylonian architects was grand and imposing.  Even now, in their desolation and ruin, their great size renders them impressive; and there are times and states of atmosphere under which they fill the beholder with a sort of admiring awe, akin to the feeling which is called forth by the contemplation of the great works of nature.