PHYSIOGRAPHY OF EASTERN PERSIA. 229
Evidences of the strength of the wind and the paucity of rain abound everywhere. In many parts of the Helmund delta the fierce " Wind of One Hundred
and Twenty Days" has scooped in the smooth plain great hollows 6 or 8 feet deep, ~.
20 or 3o feet wide, and hundreds of feet long. Universally the long axis is directed to the north-northwest. At first sight these hollows appear to have been formed by running water, but the testimony of the natives, the location of the depressions where no water could come, the uniform orientation, and the known force and direction of the wind unite to make it certain that they are of æolian origin. In this same region a peculiar effect was called to my notice by Mr. G. P. Tate, topographer of the Sistan Arbitration Commission. Sistan abounds in ruins made of sun-dried brick. Wherever the old walls stand in a north-and-south direction, parallel to the prevailing course of the wind, they remain standing indefinitely,
Fig. 151.—Ruins at the Mil-i-Kasimabad, near Zahidan. These mud walls are at least five hundred years old. Only those in a north-and-south direction remain standing.
although gradually worn very thin by attrition. Wherever the walls stand in the other direction, and are exposed to the full power of the wind, they are speedily blown away and disappear entirely. Thus it happens that the ruins often present the appearance shown in the illustration (fig. 15i), where numerous north-and-south walls stand intact, with almost no east-and-west walls to connect them. Besides these more unusual results, the wind plays its well-known part in beveling pebbles and bricks and in etching out and carrying away the softer parts of the rocks.
In winter the winds, although prevailingly from the northwest, are less severe and less regular than in summer. Occasional cyclonic storms are accompanied by southeast winds (St. John, p. 7), which bring the scant rainfall of the country. At its best the rainfall is sufficient to tinge the mountains with green for a few weeks in spring and to support a scanty population of villagers and nomads ; at its worst, it supports nothing but a few prickly bushes, and famine destroys unnumbered people and animals. The curse of Persia is the aridity due to the continental position of the country and to its rim of high mountains.