or sanctuaries,
of the same general character as the domed mosques, and often attached
to them.

[Illustration: FIG. 186.--HORSE-SHOE ARCH.]

From very early times the arches, in the arcades which have been
described as virtually constituting the whole structure of the simpler
sort of mosque, were pointed. Lubke claims as the earliest known and
dated example of the pointed arch in a Saracenic building, the
Nilometer, a small structure on an island near Cairo, which contains
pointed arches that must have been built either at the date of its
original construction in A.D. 719, or at latest, when it was restored
A.D. 821. The Mosque of Amrou, however, which was founded very soon
after the conquest of Egypt in A.D. 643, and is largely made up of
materials obtained from older buildings, exhibits pointed arches, not
only in the arcades, which probably have been rebuilt since they were
originally formed, but in the outer walls, which are likely, in part
at least, to be original.

[Illustration: FIG. 187.--EXTERIOR OF SANTA SOPHIA, CONSTANTINOPLE.
SHOWING THE MINARETS ADDED AFTER ITS CONVERSION INTO A MOSQUE.]

Whatever uncertainty may rest upon these very remote specimens of
pointed architecture, there is little if any about the Mosque of Ibn
Tulun, also at Cairo, and built A.D. 885, or, according to another
authority, A.D. 879. Here arcades of bold pointed arches spring from
piers, and the effect of the whole structure is noble and full of
character. From that time the pointed arch was constantly used in
Saracenic buildings along with the semicircular and the horse-shoe
arch (Fig. 186).

From the ninth century, then, the pointed arch was in constant use. It
prevailed in Palestine as well as in the adjacent countries for two
centuries before it reached the West, and there can be no doubt that
it was there seen by the Western Crusaders, and a knowledge of its use
and an appreciation of its beauty and convenience were brought back to
Western Europe by the returning ecclesiastics and others at the end of
the First Crusade.[37]

In the eleventh century the splendid Tombs of the Caliphs at Cairo
were erected,--buildings crowned with domes of a graceful pointed
form, and remarkable for the external decoration which usually covers
the whole surface of those domes. By this time also, if not earlier,
the minaret had become universal. This is a lofty tower of slender
proportions, passing from a square base below to a ci