ice of the Persian monarchs, who selected
Ecbatana for their place of residence during the hottest portion of the
year. Even at Isfahan, which is on the edge of the desert, the heat is
neither extreme nor prolonged. The hot gusts which blow from the east
and from the south raise the temperature at times nearly to a hundred
degrees; but these oppressive winds alternate with cooler breezes from
the west, often accompanied by rain; and the average highest temperature
during the day in the hottest month, which is August, does not exceed
90 deg..

A peculiarity in the climate of the plateau which deserves to be noticed
is the extreme dryness of the atmosphere. In summer the rains which fall
are slight, and they are soon absorbed by the thirsty soil. There is a
little dew at nights, especially in the vicinity of the few streams;
but it disappears with the first hour of sunshine, and the air is left
without a particle of moisture. In winter the dryness is equally
great; frost taking the place of heat, with the same effect upon the
atmosphere. Unhealthy exhalations are thus avoided, and the salubrity of
the climate is increased; but the European will sometimes sigh for the
soft, balmy airs of his own land, which have come flying over the sea,
and seem to bring their wings still dank with the ocean spray.

Another peculiarity of this region, produced by the unequal rarefaction
of the air over its different portions, is the occurrence, especially in
spring and summer, of sudden gusts, hot or cold, which blow with great
violence. These gusts are sometimes accompanied with, whirlwinds, which
sweep the country in different directions, carrying away with them
leaves, branches, stubble, sand, and other light substances, and causing
great annoyance to the traveller. They occur chiefly in connection with
a change of wind, and are no doubt consequent on the meeting of two
opposite currents. Their violence, however, is moderate, compared
with that of tropical tornadoes, and it is not often that they do any
considerable damage to the crops over which they sweep.

One further characteristic of the flat region may be noticed. The
intense heat of the summer sun striking on the dry sand or the saline
efflorescence of the desert throws the air over them into such a state
of quivering undulation as produces the most wonderful and varying
effects, distorting the forms of objects, and rendering the most
familiar strange and hard to be recognized