264 THE BASIN OF EASTERN PERSIA AND SISTAN. 
that in ridino; almost across the middle of il my horse's hoofs sank in only abont 
an inch. The whole expanse is covered with a beautifnlly crystalline deposit of 
salt, thinner on the ed<^es and thicker toward the middle, where it crackles like 
snow nnder the horse's hoofs. The smooth playa floor is divided into broad concentric 
bands which grow successively whiter and more thickly covered with salt toward 
the center. They appear to mark stages to which the water had risen during the 
last season, and have the irregular boundaries characteristic of water which stands 
on an almost level surface. To the eye the surface of the playa seems perfectly 
level, Init there is a slight slope, as is shown by a beach marking the high-water 
level of spring. At the south end this can hardly be distinguished from the floor 
of the playa, but a mile or two farther north it lies distinctly 8 or 10 feet above 
the floor. No lacustrine terraces could be detected, although the bluffs, which are 
cut in soft sandstone, dipping gently northeastward, and which sometimes reach a 
height of a hundred feet, seem to have been imdercut during a former higher stand 
of the water. The tributary valleys, however, show terraces to the number of three, 
cut partly in rock and partly in a filling of gravel. Away from the lake these 
gradually die out in the course of a few miles. They might easily be due to an 
intermittent warping by which the basin was deepened, although that would demand 
a rather complex system of movements by which a minor basin warping should be 
superposed upon the main warping demanded for the Heri Rud. A climatic origin 
is simpler, but the terraces are too poorly developed to be of great importance. 
NKMEKSAR OR THE PLAYA OF KHAP. 
Beyond the great northward bend of the Heri Rud, in the southward con- 
tinuation of the Afghan depression, the playa of Khaf — the Nemeksar par excellence — 
and its basin continue the terrace phenomena of the more northern districts, though 
the maxinnnn number of terraces is less. At the northeasten comer of the basin 
we passed three valleys, all of which show two strong terraces of the usual type, 
with heavy gravel beds covering the horizontal portions and with the vertical 
portions cut partly in the gravel and parti}- in the underljing rock. Besides these 
there were two minor terraces, scarcely worth mentioning, one between the two 
strong ones and one below. 
In the higher valleys of the pass near Chani Well, 8 or 10 miles north of the 
northeast corner of the playa, a phenomenon was noticed which is rather connnon 
in the mountains of this part of the world. The steeper valleys are filled with 
coarse gravel firmly consolidated b\- a calcareous cement, and now dissected into 
rude terraces. The deposit is closel)' analogous to the gravel of the ordinary 
terraces, but diflfers in being found in very steep ungraded valleys and in being well 
consolidated. Apparently these two features belong together, since only a well- 
consolidated deposit could retain its position under present conditions on so steep 
a slope. The gravel and terraces appear to be due to changes of climate, since they 
are found in ungraded valleys which would be wholly uninfluenced by any movement 
of uplift or warping which did not directly affect their own grade. It is highly 
improbable that earth movements, detennined as they must be by broadly acting 
and largely subterranean causes, should so adjust themselves as to accelerate all the 
