In Chaldæa, at least in certain times and at certain places, construction was more careful. In the ruin known as Babil, a ruin that represents one of the principal monuments of ancient Babylon, there is nothing between the bricks but earth that must have been placed there in the condition of mud.[176] These bricks may be detached almost without effort. It is quite otherwise with the two other ruins in the same neighbourhood, called respectively Kasr and Birs-Nimroud. Their bricks are held together by an excellent mortar of lime, and cannot be separated without breaking.[177] Elsewhere, at Mugheir for instance, the mortar is composed of lime and ashes.[178]
Finally, the soil of Mesopotamia furnished, and still furnishes, a kind of natural mortar in the bituminous fountains that spring through the soil at more than one point between Mossoul and Bagdad.[179] It is hardly ever used in these days except in boatbuilding, for coating the planks and caulking. In ancient times its employment was very general in the more carefully constructed buildings, and, as it was found neither in Greece nor Syria, it made a great impression upon travellers from those countries. They noted it as one of the characteristics of Chaldæan civilization. In the Biblical account of the Tower of Babel we are told: "They had brick for stone, and slime had they for mortar."[180] Herodotus lays stress upon the same detail in his description of the way in which the walls of Babylon were built: "As they dug the ditches they converted the excavated earth into bricks, and when they had enough, they burnt them in the kiln. Finally, for mortar they used hot bitumen, and at every thirty courses of bricks they put a layer of reeds interlaced."[181]
Those walls have long ago disappeared. For many centuries their ruins afforded building materials for the inhabitants of the cities that have succeeded each other upon and around the site of ancient Babylon, and now their lines are only to be faintly traced in slight undulations of the ground, which are here and there hardly distinguishable from the banks that bordered the canals. But in those deserts of Lower Chaldæa, where the nomad tent is now almost the only dwelling, structures have been found but little damaged, in which layers of reeds placed at certain intervals among the bricks may be easily distinguished. As a rule three or four layers are strewn one upon the other, the rushes in one being at right angles to those above and below it. Here and there the stalks may still be seen standing out from the wall.[182] Fragments of bitumen are everywhere to be picked up among the débris about these buildings, upon which it must have been used for mortar. It never seems to have been employed, however, over the whole of a building, but only in those parts where more than the ordinary cohesive power was required. Thus, at Warka, in the ruin called Bouvariia, the buttresses that stand out from the main building are of large burnt bricks set in thick beds of bitumen, the whole forming such a solid body that a pickaxe has great difficulty in making any impression upon it.[183]
Travellers have also found traces of the same use of bitumen in the ruins of Babylon. It seems to have been in less frequent employment in Assyria. It has there been found only under the two layers of bricks that constitute the ordinary pavement of roofs, courts, and chambers. The architect no doubt introduced this coat of asphalte for two purposes—partly to give solidity to the pavement, partly to keep down the wet and to force the water in the soil to flow off through its appointed channels. A layer of the same kind was also spread under the drains.[184]
In spite of all their precautions time and experience compelled the inhabitants of Mesopotamia to recognize the danger of crude brick as a building material; they endeavoured, therefore, to supplement its strength with huge buttresses. Wherever the ruins have still preserved some of their shape, we can trace, almost without exception, the presence of these supports, and, as a rule, they are better and more carefully built than the structures whose walls they sustain. Their existence has been affirmed by every traveller who has explored the ruins of Chaldæa,[185] and in Assyria they are also to be found, especially in front of the fine retaining wall that helps to support the platform on which the palace of Sargon was built.[186] The architect counted upon the weight of his building, and upon these ponderous buttresses, to give it a firm foundation and to maintain the equilibrium of its materials. As a rule there were no foundations, as we understand the word. At Abou-Sharein, in Chaldæa, the monument described by Taylor and the brick pavement that surrounds it are both placed upon the sand.[187] Botta noticed something of the same kind in connection with the palace walls at Khorsabad: "They rest," he says, "upon the very bricks of the mound without the intervention of any plinth or other kind of solid foundation, so that here and there they have sunk below the original level of the platform upon which they are placed."[188]
This was not due to negligence, for in other respects these structures betray a painstaking desire to insure the stability of the work, and no little skill in the selection of means. Thus the Chaldæan architect pierced his crude brick masses with numerous narrow tunnels, or ventilating pipes, through which the warm and desiccating air of a Mesopotamian summer could be brought into contact with every part, and the slight remains of moisture still left in the bricks when fixed could be gradually carried off. These shafts have been found in the ruins of Babylon and of other Chaldæan cities.[189] Nothing of the kind has been discovered in Assyria, and for a very simple reason. It would have been impossible to preserve them in the soft paste, the kind of pisé, we have described.
Another thing that had to be carefully provided for was the discharge of the rain water which, unless it had proper channels of escape, would filter through the cracks and crevices of the brick and set up a rapid process of disintegration. In the Assyrian palaces we find, therefore, that the pavements of the flat roofs of the courtyards and open halls had a decided slope, and that the rain water was thus conducted to scuppers, through which it fell into runnels communicating with a main drain, from which it was finally discharged into the nearest river.
It rained less in Chaldæa than in Assyria. But we may fairly conclude that the Chaldæan architects were as careful as their northern rivals to provide such safeguards as those we have described; but their buildings are now in such a condition that no definite traces of them are to be distinguished. On the other hand, the ruins in Lower Chaldæa prove that even in the most ancient times the constructor had then the same object in view; but the means of which he made use were much more simple, although contrived with no little ingenuity. We shall here epitomize what we have learnt from one of those few observers to whom we owe all our knowledge of the earliest Chaldæan civilization.