nd was rather penetrating, and his clothes, barring
a waistcoat, consisted of thin white cotton garments. Personally, I never
had occasion to make a change in my tropical clothing (I could not if I
had wanted to), nor did I ever once have to use an overcoat. But--I
seldom know what it is to feel cold.

We delayed our departure the next morning to see if the gale would abate,
but at 10 a.m. we had to venture out. One was rather at the mercy of the
wind on the hump of the camel. It did blow! The wind hampered the camels
greatly and was a nuisance all round, as one could only by an effort
remain on the saddle. The flying sand filled one's eyes and ears, and the
wind catching the brim of one's hat made such a hissing noise that one
had to find a more comfortable headgear by wrapping up one's head in a
blanket.

The desert was here absolutely flat, with some grazing for camels
(_kirri_). We were going north-east-east (70 deg. b.m.) amid low sand
hillocks and sand banks, and the Sultan Mountain still on our left in all
its glory. To the north-east (55 deg. b.m.) we had another mountain mass
lower than the Sultan and not nearly so picturesque, and before us, on
going over a gentle incline some 35 ft. above the level of the plain
(about 13 miles from Tretoh), three long rows of bright yellow,
flat-topped, crescent-shaped sand-hills stretching for several miles from
north to south were disclosed. These three rows of barchans were
parallel, and at intervals of about from 300 yards to 500 yards from one
another. The barchans averaged from 50 ft. to 100 ft. in height. Another
row of them stretched along the foot of the mountain range to the north
and extended from north-west to south-east.

The cause of these extensive parallel rows of barchans was to be found in
gaps in the hills to the north between the Sultan, the next range, and
two intervening obstacles in the shape of a low mound and a great rock,
the sand being blown through the interstices and gradually accumulating
in the plain on the south.

On that march we saw a most extraordinary effect of mirage. To the east
(100 deg. b.m.) the peculiar flat-topped Gat (or Gut) Mountain, which looked
like a gigantic lamp-shade, could be seen apparently suspended in the
air. The illusion was perfect, and most startling to any one with
teetotal habits. Of course the optical illusion was caused by the
different temperatures in the layers of air directly over the earth's
surface and t