The masons of Babylon and of other southern cities made a much more extensive use of burnt brick than those of the north. In Assyria the masses of pise have as a rule no other covering than the slabs of alabaster and limestone, and above, a thin layer of stucco. In Chaldaea the crude walls of the houses and towers were cuirassed with those excellent burnt bricks which the inhabitants of Bagdad and Hillah carry off to this day for use in their modern habitations.[173] The crude bricks used behind this protecting epidermis have not lost their individuality, as at Nineveh they seem to have been used only after complete dessication. They are of course much more friable than those burnt in the kiln; when they are deprived of their cuirass and exposed to the weather they return slowly to the condition of dust, and their remains are seen in the sloping mounds that hide the foot of every ancient ruin (see Fig. 48), and yet if you penetrate into the interior of a mass built of these bricks, you will easily distinguish the courses, and in some instances the bricks have sufficient solidity to allow of their being moved and detached one from another. They are, in fact, bricks, and not pise. But in Chaldaea, as in Assyria, the mounds upon which the great buildings were raised are not always of crude brick. They are sometimes made by inclosing a large space by four brick walls, and filling it with earth and the various _debris_ left by previous buildings.[174] Our remarks upon construction must be understood as applying to the buildings themselves, and not to the artificial hills upon which they stood. [Illustration: FIG. 48.--Temple at Mugheir; from Loftus.] The Assyrians seem never to have used anything analogous to our mortar or cement in fixing their materials. On the comparatively rare occasions when they employed stone they were content with dressing their blocks with great care and putting them in absolute juxtaposition with one another. When they used crude brick, sufficient adherence was insured by the moisture left in the clay, and by its natural properties. Even when they used burnt or well dried bricks they took no great care to give them a cohesion that would last, ordinary clay mixed with water and a little straw, was their only cement.[175] Even in our own day the masons and bricklayers of Mossoul and Bagdad are content with the same simple materials, and their structures have no great solidity in consequence.