APPENDICES 381

Calcareous deposits on a more extensive scale evidently once
occurred at *Ain Sala. Here Mr. Philby collected a large number
of roughly cylindrical pieces of tufa, each encasing a perfectly
cylindrical smooth-walled tube. The tubes measure from 1-2 cm.
in diameter and reach 15 cm. in length. They have quite smooth
inside walls and are usually uniform in diameter from beginning
to end. Some pieces of tufa contain more than one tube ; and in
such cases the tubes are nearly parallel or very slightly diverging.
The outer surfaces of the pieces of tufa, while approximately
cylindrical, are uneven and very porous like typical calcareous
tufa or travertine. Some are partly smoothed and a little polished
by wind action.

For some time no clue could be obtained as to what had caused
these tufa-cased tubes. Roots and plant stems were suggested,
but the tubes seemed too smooth and too straight and uniform
in diameter for these. The explanation was by a fortunate chance
supplied by Colonel J. K. Robertson, who remembered having
seen similar tubes in calcareous tufa from Trans-Jordan. At his
suggestion a specimen has been kindly presented to the British
Museum by Mr. J. E. G. Palmer. It consists of a stem of the
reed Arundo, 14 mm. in diameter, completely encased for over
40 cm. of its length in a cylindrical casing of calcareous tufa, with
a radiating structure. When pulled clear of the reed stem the
inside of the tube is seen to be perfectly smooth and very uniform
in diameter. At the nodes there are swellings in the outer sur-
face of the tufa casing. When Mr. Philby's hollow cylinders are
compared with this specimen, there is no possibility of doubting
that they too are the casings of reed stems.

The specimen from Trans-Jordan was found by one of Messrs.
Rendel, Palmer & Tritton's engineers in the bed of Wadi Zahar,
a tributary of Wadi al 'Arab, on the eastern escarpment of the
Jordan valley.

From this identification, and from the abundance of the hollow
cylinders lying scattered about, one must conclude that a reed
bed grew at 'Am Sala at no very distant (geological) date. One
may perhaps associate this reed bed with the period at which
lived the fresh-water shells mentioned in Mr. Cox's report, for at
one of the localities for these, namely Abu Muhairat, Mr. Philby
collected also a single specimen of tufa showing the hole left by a
reed stem. This is so far the only other record of these interesting
relics of moister times.

Gypsum.—In the form of surface crusts gypsum seems to be
widespread over parts of Mr. Philby's route. Fine-grained
'gypseous tufa' was collected at Dharbun, *Uj and Bir ibn
Juhaiyim. At the first-named locality it overlies a pink sand-