I. ©. Russell—The Jordan-Arabah and the Dead Sea. 391 
The first hypothesis is that the strait separating the Lisan penin- 
sula from the west shore of the Dead Sea was formerly contracted 
so as to partially shut off the southern end of the lake from the main 
water body, and that evaporation in the restricted basin thus formed 
was greater than the amount of water contributed to it by streams 
and springs. The result of these conditions would be an influx of 
water from the main or northern water body and a deposition of salt 
in the partially inclosed southern basin. If this process continued 
for a considerable time, a heavy deposit of salt would result, which 
might become buried beneath lacustrine marls when an increase 1n 
humidity caused the two basins to unite. In this manner the great 
deposit of salt along the south-west border of the Dead Sea with its 
covering of marl, as well as the absence of similar saline deposits in 
other portions of the basin, can, apparently, be accounted for. 
The sequence of events here postulated is suggested by the 
topography of the shores of the Dead Sea. As indicated on the 
maps accompanying the reports of the U. 8. Expedition, the strait 
referred to in the above paragraph is two miles wide and from 
twelve to eighteen feet deep. The area south of this contraction, and 
now partially shut off from the main body of the Dead Sea, has a 
surface sixty square miles in extent. If this basin should be filled 
to the horizon of the highest salt deposits at Jebel Usdum, its area 
would probably exceed a hundred square miles. A contraction or 
filling of the strait connecting the two divisions of the sea, as sug- 
gested above, possibly by the construction of embankments across it, 
would initiate conditions similar to those now to be observed on the 
east shore of the Caspian, where a gulf known as the Kara Bugaz 
furnishes an evaporating basin for the waters of the main sea. In 
this instance the amount of water reaching the Kara Bugaz annually 
through streams and springs, etc., is much less than the mean annual 
evaporation from its surface, consequently a current flows continually 
from the Caspian into the gulf. Owing to these peculiar conditions 
a precipitation of salt is taking place from the highly concentrated 
waters of the gulf, while the main water-body contains only a small 
fraction of one per cent. of saline matter in solution. Should the 
Caspian rise a few hundred feet, the Kara Bugaz would have free 
communication with the main sea, and the beds of salt in its bottom 
would become covered with lacustrine sediments, probably charged 
with freshwater shells. The record thus produced would be essen- 
tially the same as the section now exposed on the south-west border 
of the Dead Sea. 
The second hypothesis is that the Dead Sea basin throughout was 
far more shallow than at present at the time of the deposition of the 
rock salt and gypsum on its south-west border, and that subse- 
quently it rose sufficiently to bury these deposits beneath lacustrine 
sediments. After this rise a movement took place along the Jordan- 
Arabah fault and deepened the basin; or, it may be suggested, that 
the change was due to the subsidence of an orographic block 
situate beneath the Dead Sea, and included between the main fault 
and a secondary fracture branching from it. At a later date the 
