'Report by Mr G P Tate, Extra Assistant Superintendent, Survey of India, in charge of the survey detachment with the Seistan mission, 1903-05.' [‎2v] (4/16)

whole difference between the side Koh Khwaja to Sabzkim, computed from
the triangulation of Seistan ; and from the side Koh-Malik-Siah to Koh-Khwaja,
is 14 feet in a length of 20 2 miles. A second comparison was made further
to the south, on the side Koh-Malik-Siah to the interpolated station Tump-i-
Mir Dost. In 1899 the latter was fixed for purposes of plane-tabling alone ; by
observations to three known points, the centre point being Koh-i-Malik Siah.
In 1904-05, this station of Tump-i-Mir Dost was connected with Koh-
i-Malik Siah by triangulation, the angle at Koh-i-Malik Siah having been un
observed, and also every acute. The whole difference in length of the side Koh-
i-Malik Siah to Tump-i-Mir Dost, from the triangulation of 1899 and 1904-05,
respectively, is 200 feet in a distance of 39 miles.
The triangulation in the direction of the Koh-i-Malik Siah was carried on by
Surveyor Jamaludin. It was not possible for me to be away from the main camp,
for many reasons, and as I had also to lay down the straight lines of boundary
pillars between points such as the Koh-i-Malik Siah and B. P. No. 51, close to
the bifurcation of the Rud-i-Seistan and the Helmand (a distance of 86 miles),
as well as further on towards the northern terminus of the boundary, the trian
gulation towards the south was left to the Sub-surveyor just named, who carried
it on satisfactorily until he was disabled by a fall from a restive riding camel
owing to which he had to return to camp. It was due to this tnangulation that
the extension, desired by the British Commissioner, towards the south, of the
detail surveys on the scale of i"=i mile was rendered possible.
The surveys on the scale of t v =4 miles were extended on all sides as far
as possible, and every opportunity was taken advantage of in order to increase
the area of this work. Thei"=i mile surveys were ordered by the British
Commissioner in order to elucidate problems connected with the changes that
have taken place in the course of the Helmand from Bandar-i-Kamal Khan
downwards, in the past, as well as those which are now in progress.
The delta of the Helmand actually begins at Bandar-i-Kamal Khan, and
it was necessary to place on record, graphically, the various old channels that
had once contained the river. There were also questions affecting these old
channels and the possibility or otherwise of their being revived, by the con
structions of weirs or dams across the river, or any attempts to tamper with its
present course. Such points could only be dealt with satisfactorily when the detail
had been rendered on a scale on which the irrigation officer was able to plot his
levels. It was also considered to be necessary for military purposes. The British
Commissioner desired it to be continued to theShela, the channel of communica
tion between the present Hamun of Seistan, and the older Hamun known now as
the Gaud-i-Zireh (the Hollow of Zireh). The accident to Surveyor Jamaludin,
however, put a stop to this extension, as it was not considered advisable for me
to visit those tracts, and there was no one else to do the work. Trigonometrical
points were needed in order to keep the work up to the same standard as to •
• A comparison was made in Seistan between heights obtained trigonometrically and others obtained
by two Boiling point thermometers, and with a height taken carefully, in 1885, by the Afghan Boundary
Commission, with a mountain Barometer. The trigonometrical heights show a defect of (in round
numbers) 90 feet compared with both of the latter which appear to be fairly accordant. Trigonometrical
heights were carried on by means of reciprocal vertical angles from the triangulation to the south of the
Helmand executed bv the Survey officers of the Afghan Boundary Commission in 1885.
The Irrigation officer connected his levels with Koh-i-Khwaja h. s. and the trigonometrical heights in
Seistan also depend on the height of that station above mean sea level. Refraction in Seistan is very-
great and in its effect is of opposite signs.