"نجد الجنوبية: رحلة إلى الخرج والأفلاج والسليل ووادي الدواسر في سنة ١٩١٨." [و‎‎٣‎٢] (١٠٠/٦٨)

With reference to these figures it is interesting to note that
the treasury share of dates from Saih (in the Aflaj), where the
rate of tax is ten per cent owing to its possession of facilities
for perennial flow irrigation, amounted two years ago to
46,000 Sas.
As regards the climate experienced during the period between
May 23 when I reached Sulaiyyil and June 6 when I finally
quitted the wadi area, a period, it should be noted, when at this
latitude* and at this time of the year the sun was practically
vertically overhead at noon, my general impression was that it
was surprisingly agreeable. The maximum temperature recorded
during this period was llO'S F. on May 26 at Tamra, while
on two occasions in the wadi the 100 degrees mark was not
reached ; on the whole the wadi maximum temperature ruled
lower than those recorded during the days spent at Sulaiyyil,
Tamra, and Kimida, the average maximum during the first
seven days being between 108° aud 109°, while that of our
sojourn at the wadi was only 102° and would have been consider
ably lower but for a reading of 107 - 6 o on June 3. The appearance
of the Pleiades is, whether rightly or wrongly I cannot say,
as signed locally as the cause of the sudden modification of the
temperature. The maximum temperature registered was actually
only 64° F. on the last day of the period, but the next lowest
figure was 70° with an average of about 72°, while during the
days spent at the wadi itself I was generally not up early enough
to record a proper minimum. The prevailing wind throughout
the period was from the north with occasional sudden changes
to all the other points of the compass. From this record it will
be seen that the climate conditions of the south are far from
irksome—a fact on which the people of the wadi pride themselves
not a little as also on the extreme dryness and purity of their
atmosphere.
On the afternoon of June 5 we said goodbye to the Amir
and retraced our steps past the northern wall of Dam, now no
longer interested in our doings, down the valley to Raka, where
we camped for the night; and on the following day we made a
serious start on our long return journey, steering straight for
the northern barrier of Tuwaiq at first ENE. and later north-east
over the rolling Nafudh, known vaguely as Qaas, which by
gradual degrees developed into a sandy plain. In due course
* Roughly Lat. 21" N.