1919. | Seistan and the Helmand. II 
Eastern Persia and the neighbouring countries have become desic- 
cated in the recent period, we may be certain that the basin of 
the Helmand contained more water at a period geologically not 
remote than it does now. More water must have entered the 
river, there must have been less loss by evaporation and possibly 
less by absorption in recent alluvium. Moreover, the structure of 
the Afghan-Baluch desert leaves little doubt that lakes of consider- 
able area once existed within its confines, even if it never formed 
a single great lake-basin. It needs no great exercise of the ima- 
gination, for example, to believe that the Gaud-1-Zirreh, which is 
over eighty miles long and some twenty miles broad, was once a 
comparatively deep lake, which gradually silted up, as most lakes 
do in the course of time. Further, the clay of which the cliffs at 
J,ab-i-Baring at the edge of the Hamun-i-Sabari (antea, p. 7) are 
composed has all the appearance in its fine texture, uniform struc- 
ture and lack of stratification, of being a lake deposit.! My friend 
Mr. EK. Vredenburg of the Geological Survey of India, who has 
been kind enough to examine specimens of this clay, reports that 
they closely resemble that of certain tertiary deposits in the Siwa- 
liks which he believes to be of lacustrine origin. I have pointed 
out above (p. 8) that, except in being totally devoid of animal 
remains, it closely resembles the deposit now being formed at the 
bottom of the Hamun in the immediate vicinity of the cliffs.? 
This, however, does not prove that the existing Hamun is the 
actual remains of an ancient freshwater lake. All that it indicates 
is that the Hamun occupies part of an old lake-basin. As the 
cliffs are over fifty feet high, this old basin must have contained a 
large body of water and existed for a long period, in order that so 
much silt should have been deposited. 
The structure of the cliffs at this place is uniform except for a 
layer of a few feet on the surface. ‘This layer is composed of dry 
earth more friable than the clay beneath it and full of water-worn 
pebbles, either of limestone or of volcanic origin. The following 
report on specimens of the limestone pebbles by Mr. Vredenburg 
shows that they do not differ from those found in the neighbour- 
ing desert* (with which this layer is, indeed, in continuity both 
structurally and geographically), and that, therefore, they have 
been brought from distant hills by occasional floods and not 
shaped by the waves of a lake. Mr. Vredenburg writes :— 
““The three pebbles of dark-grey limestone contain a few 
specimens of Nummulites atacicus, Leym., a fossil characteristic of 
Geology in Eastern Persia, pp: 448-451, may also be consulted and the reports 
of the Expedition to Central Asia organized by the Carnegie Institution of 
Washington. 
! Huntington, of. cit., 1905, p. 285. 
2 It should be noted in this connection that in the Siwaliks proper of the 
sub-Himalayan area, which were not formed under desert conditions, freshwater 
fossil shells are abundant at certain places. Precise information about the species, 
etc., is, however, still lacking. 
8 See Blanford, op, cit., p- 465 (London, 1876), and Vredenburg, of. cit., 
p- 189. 
