, are also surprising. By careful
moulding and manipulation the Assyrian builder made his brick voussoirs as
well fitted for their work as the cut stone of our day. Each brick had its
own shape and size, so that it was assigned in advance a particular place
in the vault and its own part in assuring the final stability of the
building. In all this we cannot avoid seeing the results of a patient and
long-continued process of experiment and education carried on through many
centuries in all the workshops of Mesopotamia.

The art of building vaults with small units of construction was, then,
carried farther in Mesopotamia than in Egypt; it was there more frankly
developed; it was there forced with greater success to supply the place of
stone and timber. It was in fact more of an indigenous art in the valley of
the Tigris and Euphrates than anywhere else, more inspired by the permanent
and unchanging conditions of the country--in a word, more national.

In these days the historian sets himself with devotion to follow in all its
involutions the long chain of thought and effort by which man has been led
from his primitive barbarism to the well-being of modern civilization, and
to his domination--every day more complete and more intelligent--over the
minor forces of nature. It is the duty of criticism, as its methods
gradually perfect themselves, to add daily to its perspicacity and powers
of observation, and to lessen as much as possible the occasions, still so
numerous, when the thread of evidence breaks in its hands and the true
relations of facts to each other become obscured. Even yet we cannot say
for certain to which nation of the ancient world the invention of the arch
belongs. In those remote ages the principle may have been discovered more
than once or twice in different and distant countries whose inhabitants
were busied over the same task. We have no reason to believe that Chaldaea
learnt the secret from Egypt, or Etruria from the East. It is none the less
true, however, that the unknown architects of Babylon and Nineveh made full
use of it at an earlier date and in more intelligent fashion than any of
their rivals. To them must be given the credit of being the masters and
art-ancestors of the men who built the Pantheon and the Church of Saint
Sophia, Santa Maria del Fiore, and Saint Peter's in Rome, and more
especially of those great modern engineers to whom the principle of the
arch has been a chief element in thei