388 TI. O. Russell—The Jordan-Arabah and the Dead Sea. 
usually referred to as lake terraces, seem to admit of another inter- 
pretation. 
The Dead Sea basin has been deeply filled, especially in its northern 
and southern portions, by lacustrine sediments, supplemented by gravel 
and sand washed from tributary valleys and neighbouring alluvial 
slopes. It seems probable that these deposits filled the basin from 
side to side in the Jordan valley and in the Wady Arabah, but not so 
completely as to form a level floor throughout. When the waters of 
the ancient lake fell to a lower level than the surface of the sedi- 
ments in question, the Jordan flowing from the north and the Jeib 
from the south, toward the Dead Sea, cut channels in the previously 
formed deposits. Pauses in the lowering of the lake surface would 
establish a base level of erosion for the inflowing streams, thus allow- 
ing them to widen their channels, so that when another lowering of 
the lake occurred and the streams re-commenced the excavation of 
their channels, a terrace would be left on the sides of their valleys. 
These terraces would slope with the grade of the streams which 
formed them, and on reaching the Dead Sea basin, would unite with 
the horizontal terraces formed by the waters of the inclosed sea. 
This interpretation of the history of the terraces of the Jordan 
valley is strengthened by the following observation recorded by Hull 
in the narrative of his journey of exploration.’ ‘All these terraces 
(along the Jordan near Jericho), excepting perhaps the upper, have 
doubly sloping surfaces, both toward the centre of the valley and 
toward the Salt Sea. The upper terrace only slopes toward the 
centre of the valley, as its upper surface corresponds almost exactly 
with the terrace of Jebel Usdum, and the other old sea margins, near 
the southern end of The Ghér.” 
Sections of the material filling the Wady Arabah near the steep 
descent to the plain of the Dead Sea show fine lacustrine sediment at 
the base, passing into sand and gravel in the upper portion. The 
surface of this deposit rises when followed southward or up the 
valley, but breaks off abruptly, as mentioned above, in a steep 
escarpment about six hundred feet high at the north, facing the 
depression now holding the Dead Sea. The structure of this deposit 
so far as known, as well as its topographic form, suggests the pro- 
bability that it is of the nature of a delta, the steep lakeward scarp 
of which has been cut away by the waves and currents washing its 
base. A similar interpretation will apparently apply in many ways 
to the facts reported concerning the material filling the Jordan 
valley. <A detailed study of these deposits is required, however, 
before the mode of their formation can be definitely determined. 
Lake beds are mentioned by Hull, and others, as existing not 
only in those portions of the basin adjacent to the Dead Sea, but at 
high altitudes near both the northern and southern portions of its 
basin. In Wady Arabah fine, evenly stratified lacustrine sediments 
charged with freshwater shells, were observed at an elevation of 
1400 feet above the present surface of the Dead Sea.* In the same 
1 “ Mount Seir, Sinai and Western Palestine,”’ p. 162. 
* Geol. and Geog. of Arabia Petraa, Palestine, etc., p. 80. 
