thin the walls of each chamber;
finally, the singular thickness of the walls, which is only to be
satisfactorily explained by the supposition that the architect had to
provide solid abutments for arches that had no little weight to carry.

It is difficult to say how the Assyrians set about building these arches of
crude brick, but long practice enabled their architects to use that
unsatisfactory material with a skill of which we had no suspicion before
the exhumation of Nineveh. Thanks to its natural qualities and to the
experienced knowledge with which it was prepared, their clay was tough and
plastic to a degree that astonished the modern explorers on more than one
occasion. The arched galleries cut during the excavations--sometimes
segmental, sometimes pointed, and often of a considerable height and
width--could never have stood in any other kind of earth without strong and
numerous supports. And yet M. Place tells us that these very galleries,
exactly in the condition in which the mattock left them, "provided lodging
for the labourers engaged and their families, and ever since they have
served as a refuge for the inhabitants of the neighbouring villages.
Workmen and peasants have taken shelter under vaults similar to those of
the ancient Assyrians. Sometimes we cut through the accidental
accumulations of centuries, where the clay, far from having been carefully
put in place, had rather lost many of its original qualities. Even there,
however, the roof of our galleries remained suspended without any signs of
instability, as if to bear witness that the Assyrian architect knew what he
was about when he trusted so much to the virtues of a fictile
material."[202]

We may refer those who are specially interested in constructive methods to
M. Place's account of the curious fashion in which the workmen of Mossoul
will build a pointed vault without the help of any of those wooden
centerings in use in Europe. In our day, certainly, the masons of Mossoul
use stone and mortar, but their example none the less proves that similar
results may once have been obtained in different materials.[203] A vault
launched into mid-air without any centering, and bearing the workmen who
were building it on its unfinished flanks, was a phenomenon calculated to
astonish an architect. Taking everything into consideration the clay vaults
of Khorsabad are no more surprising than these domes of modern
Mossoul.[204]

We cannot say for certain that