n Arabia, and at its northern end many outlying spurs and
detached _mesas_ remind the traveller of the Abyssinian hills--known as
_ambas_. A portion of this singular territory belongs to the great
gypsum formation of the south-western prairies, perhaps the largest in
the world; while a highly-coloured sandstone of various vivid hues,
often ferruginous, forms a conspicuous feature in its cliffs. Along its
eastern edge these present to the lower champaign of Texas a precipitous
escarpment several hundred feet sheer, in long stretches, tending with
an unbroken facade, in other places showing ragged, where cleft by
canons, through which rush torrents, the heads of numerous Texan
streams. Its surface is, for the most part, a dead horizontal level,
sterile as the Sahara itself, in places smooth and hard as a macadamised
road. Towards its southern end there is a group of _medanos_
(sandhills), covering a tract of several hundred square miles, the sand
ever drifting about, as with _dunes_ on the seashore. High up among
their summits is a lakelet of pure drinking water, though not a drop can
be found upon the plateau itself for scores of miles around. Sedge and
lilies grow by this tarn so singularly situated.

Here and there the plain is indented by deep fissures (_barrancas_),
apparently the work of water. Often the traveller comes upon them
without sign or warning of their proximity, till, standing on the edge
of a precipitous escarpment, he sees yawning below a chasm sunk several
hundred feet into the earth. In its bed may be loose boulders piled in
chaotic confusion, as if cast there by the hands of Titans; also trunks
of trees in a fossilised state such as those observed by Darwin on the
eastern declivity of the Chilian Andres.

Nearly all the streams that head in the Staked Plain cut deep channels
in their way to the outer world. These are often impassable, either
transversely or along their course. Sometimes, however, their beds are
worn out into little valleys, or "coves," in which a luxuriant
vegetation finds shelter and congenial soil. There flourish the pecan,
the hackberry, the black walnut, the wild china, with evergreen oaks,
plums, and clustering grapevines; while in the sterile plain above are
only seen those forms of the botanical world that truly indicate the
desert--various species of cactaceae, agaves, and yuccas--the palmilla
and lechuguilla, dwarf-cedars, and mezquites, artemisia, and the
strong