244	THE EMPTY QUARTER
Upstream of the dyke the wind had scooped out a deep pit,
in whose sandy bottom we found two wells known as Bir ibn
Suwailim after our Dimnani guide, Salim ibn Suwailim, who
had originally dug them out about 25 years ago, when these
southern sands would seem to have enjoyed their last con-
siderable cycle of good rains and good pastures. Subse-
quently drought had driven the Arabs and their camels else-
where, and Salim's wells, left to their fate, had been swallowed
up by the sands until their site was rediscovered and cleared
in the 1929-30 season by 'Ali Jahman, truly a great desert
pioneer. As at Arfaja the water was found to be similar in
quality to that of Shanna, but its depth was nine fathoms—
a fact that suggests that the diggers at Arfaja might have
met with better success if they had sunk their shaft to, say,
10 fathoms. After a single season's use the tribesmen
moved away from the watering of Ibn Suwailim, and again
the sands did their work upon the site.
The valley now ran up in a southerly direction through a
maze of dunes rising from the desert floor to heights of 200
or 300 feet and scattered about and across the trough in
little groups of two and three. Here and there a small patch
of the exposed bedrock attracted our attention, while after
labouring along, up hill and down dale, in a most tiring
manner for about three miles we found ourselves on the 300
feet summit of a steep sand-slope with the pit of Mamura
immediately below us. 'Ali had done his best to persuade me
to march direct from Bir ibn Suwailim to Zuwaira in order
to avoid this difficult patch of country, but I had explained
to him that it was absolutely necessary for me to see a
locality with my own eyes if I wished to place it on the map.
So hither we had come.
A hare—one of a dozen we encountered during this day's
march through comparatively good pastures—went away as
we descended into the bottom, where we found several
lizards for my collection. A party of Murra had occupied
this locality during the season of 1929-30—the 'day of Sibila^5
as it is called in Arabian chronology after the great battle
near Zilfi which gave Ibn Sa'ud the final victory over the
rebel Ikhwan—and 'Ali, prospecting as always for water, had