Tristram— Valley of the Jordan. 255 
which could not be well illustrated except by photographs. This 
plain itself is a soapy marl, and at a slight depth below the surface 
presents the appearance of a rich loam; but the only plants existing 
were two species of Salsola. 
This deposit of marl, extending all round the shores of the Dead 
Sea, and up the Wadys which open into it, forms the chief feature 
in the geology of the district. Above it, three water-worn terraces, 
corresponding on both sides of the Ghor, can be distinctly traced in 
the Cretaceous cliffs. 
South of the Wady Dabur, at the north-west end of the Dead Sea, 
a mass of igneous rocks crops out of the hills like a dyke, in three 
ridges, cutting through the gravel at an angle of 70 or 80 degrees. 
The cliffs above the slopes generally consist of a sandy limestone, 
very variable in its texture, and frequently mixed with conglome- 
rate, containing pebbles of all sizes. Near Feschkah a basaltic dyke 
runs NE. and SW. Four hot sulphurous springs occur between 
Ras Feschkah and the south-west end of the Dead Sea, at a short 
distance from the shore; the temperature of the water in some of 
them rises to 120° Fahr., and sensibly affects that of the sea at a 
distance of many yards. 
Mr. Tristram then described the hill of Jebel Usdum, which is a 
huge ridge of salt, about a mile wide, and running NE. and SW. 
for a distance of three miles and a half, then due N. and S. for four 
miles further; it is situated near the southern extremity of the 
Dead Sea, and renders that end of it much more salt than the 
northern portion. Further, the author thinks that it is the proxi- 
mate cause of the saltness of the Dead Sea, the drainage to which 
has been dissolving away portions of the salt, and carrying it to the 
Dead Sea, ever since the elevation of the ridge of Akabah separated 
the latter from the Red Sea, or since the dessiceation of the ocean, 
which existed to the Eocene Period, presuming (which seems most 
probable) that the fissures of the Ghor were of submarine origin, and 
that the valley itself was during the Tertiary Period the northern- 
most of a series of African lakes, of which the Red Sea was the next. 
The volume of the Dead Sea from that time continually decreased, 
by the evaporation of its water, probably to the time of the Glacial 
Epoch, of which we find traces in the Lebanon and elsewhere, so 
that two causes have combined to increase the intensity of its salt- 
ness, which is still becoming greater, though the volume of water 
has probably been in equilibrium since the termination of the Vol- 
eanic and Glacial Epoch. Sulphur and gypsum are associated with 
salt at the foot of Jebel Usdum; and there is an extensive deposit of 
sulphur and bitumen in the Mahawat Wady, two miles SW. of the 
Dead Sea. 
The author then gave a general sketch of the geology of Palestine. 
The Lower Cretaceous period is the only one represented by sedi- 
mentary rocks; but in the north-east, in the Lejah district, voleanic 
rocks occur abundantly; and Mr. Tristram concluded his paper by 
describing the extinct volcanos, and the ancient lava-streams of the 
valley of the Hieromax, the shores of the Sea of Galilee, and other 
portions of the North of Palestine. 
