"نجد الجنوبية: رحلة إلى الخرج والأفلاج والسليل ووادي الدواسر في سنة ١٩١٨." [و‎‎٤‎٤] (١٠٠/٩٢)

— 79
and soon found ourselves once more in view of the palms of
Hair. At Hair, reached after a total march of 293 miles from
the wadi, we camped for the night finding but little change
from the state in which we had left it a month and a half before,
except that the dates had increased in size though they were
still far from ripe, while the stream had ceased to flow and
the pond had sunk to less magnificent proportions.
My aneroid, whose highest reading on the previous occasion
had been 1,800 feet above sea-level, now gave a minimum
reading of 2,050 feet, though a comparison of the climatic
conditions prevailing on either occasion might lead one to expect
a reversal of the record, my weather notes on the first occasion
showing a south wind, distant thunderstorm and a very small
fall of rain, while on this occasion day and night were uninter
ruptedly fine with a good deal of north wind. The following
comparative table of thermometer readings recorded on the
two occasions shows the rise in temperature which had taken
place in the interval between our two visits :—
While on the subject of climate it will be convenient to make
a brief survey of the weather conditions found to obtain on the
Tuwaiq plateau from June 7, when I entered it at its southern
end, to June 23, when I arrived at Hair. The period falls into
two well marked divisions, the day on which we passed the nor
thern boundary of the Afiaj hill district bringing a complete
change both in the temperature and in general climatic conditions.
With so little in the way of data to go upon it is difficult to say
whether this difference is a permanent feature or not, but it
seems to me, both from my own observations and from popular
ideas on the subject, not unlikely that there is a well-marked
line of more or less permanent differentiation between the
climates of the upper and lower districts of Southern Nejd, the
boundary between these two divisions for these purposes seeming
to me to run from the Hunnu Shaib on the south of the Afiaj
plain district along the slope of Tuwaiq between the hill and
Time.
7.0 p.m.
May 6 to 7.
89-96
87-44
83-48
71-96
June 23 to 24.
98-6
95-9
87-8*
78-98
4.30 a.m.
* At 11.30 p.m. the temperature had suddenly dropped to 79-16.