In the most ancient of the Chaldaean edifices we occasionally find, as in the Bowariyeh ruin at Warka, the entire structure composed of the inferior material; but the more ordinary practice is to construct the mass of the building in this way, and then to cover it completely with a facing of burnt brick, which sometimes extends to as much as ten feet in thickness.

The burnt brick was thus made to protect the unburnt from the influence of the weather, while labor and fuel--were greatly economized by the employment to so large an extent of the natural substance.

The size and color of the bricks vary.
The general shape is square, or nearly so, while the thickness is, to modern ideas, disproportionately small; it is not, however, so small as in the bricks of the Romans.

The earliest of the baked bricks hitherto discovered in Chaldaea are 11 1/4 inches square, and 2 1/2 inches thick, while the Roman are often 15 inches square, and only an inch and a quarter thick.

The baked bricks of later date are of larger size than the earlier; they are commonly about 13 inches square, with a thickness of three inches.