Page:1902 Encyclopædia Britannica - Volume 27 - CHI-ELD.pdf/431

 DEAD 300 m. is 27'8 per cent, of the weight, and consists of chlorides of calcium, magnesia, sodium, and potassium, and in smaller proportions of bromides and sulphates of the same substances. The richness in bromine is held to indicate greatly prolonged concentration. Eggs float in the water. Curative properties were attributed to it in Roman times; and according to Mukaddasi, a.d. 985, people assembled to drink it on a feast day in August. A bath in the lake is wholesome and refreshing. The oily sensation after bathing is due to the chloride of calcium ; and the noisome, acrid taste to the chloride of magnesia. The chloride and bromide of magnesia are fatal to all animal life excepting certain microbes found in the mud by Ehrenberg and Lortet. Fish carried down by the Jordan, and small fish from brackish pools and streams near the shore, die at once in the water of the lake. The water strongly affects the eyes, and evaporation leaves a thick deposit of salt. The water is limpid and transparent, and under varying conditions is deep blue or green in colour. Its surface, far from being motionless, as some writers have supposed, is constantly rippled by breezes, or raised into waves by the strong northerly winds, and is sometimes veiled by light bluish clouds or haze produced by the evaporation. Molyneux, in 1847, and others since that date, have noticed a streak of white foam which sometimes stretches from the north-west end of the lake towards el-Lisan, following nearly the axis of the lake. From this Blanckenhorn concludes that there is a sub-lacustrine fissure which he considers to be thermal and asphaltic; but the phenomenon is possibly due to the current of the Jordan, which does not expend its force completely until it reaches el-Lisan. A recent traveller, Rev. P. Cady, writes of a strong current setting towards the north along the east coast; of oil floating on the water near the mouth of the Zerka Ma'in; and of disturbances of level that appear, like those to which the Lake of Geneva is subject, to be due to differences of barometric pressure at different points on the lake. The origin of these and other phenomena can only be ascertained by a thorough scientific examination of the lake and its basin. The shores are sterile and desolate from the absence of fresh water, and from the smallness of the rainfall, and not, as formerly supposed, from the poisonous nature of the air. The springs near the lake give life to thickets of willow, tamarisk, and acacia, which are frequented by birds; and wherever, as at Engedi, there is running water the vegetation is almost tropical in its luxuriance. The plain of Jericho is very fertile, and south of the lake the Arabs raise crops of wheat, dura, cotton, and tobacco. The climate in summer and autumn is very hot and unhealthy; but in winter it is good, with hot days and cool nights. The unhealthiness is due partly to the intense heat, and partly to the miasma from the swamps and lagoons at the southern end. The scenery is remarkable for the brilliancy of the colouring, and the varying effects of light and shade. The abrupt slopes on either side, the deep ravines on the eastern shore, and the intense colouring of the water combine to form a scene of grandeur and beauty which has been compared, not inaptly, with the aspect of some portions of the Lake of Geneva. Boats were employed on the lake in Roman, and possibly in much earlier, times (Tacitus, Hist. v. 6; Josephus, Ant. ix. 1, § 2 ; B. J. iv. 7, § 6) ; they are represented on it in the mosaic map at Medeba; and under the Latin Kingdom of Jerusalem the navigation dues formed part of the revenue of the Lords of Kerak. The use of boats died out when the Turks abandoned the country east of the Jordan to the Bedawfn. During the 19 th century boats have occasionally been used for exploration, and since the occupation of Moab and Edom

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by the Turks an attempt has been made to place small steamers on the lake. Name.—In the Old Testament the Dead Sea is called “the sea,” the “salt sea,” the “sea of the Arahah,” and “the eastern sea.” The name “Dead Sea” appears in the Vulgate (Jos. iii. 16), and is used by Pausanias, Galen, Justin, and Eusebius. Diodorus Siculus, Pliny, and Josephus call it the “Asphaltic Lake,” and others the “Sodomitish sea.” It is now known to the Arabs as Bahr Liit, “ the sea of Lot,” Geology.—The Jordan-Araba depression, in which the Dead Sea lies, was produced by subsidence along a line of faults or fractures during the terrestrial movements that accompanied the gradual elevation of the region out of the sea after the close of the Eocene period. As a result of the faulting, the formations on the opposite sides of the lake do not correspond. Whilst the hills on the western side are formed entirely of Cretaceous limestones, the abrupt face of the Moabite plateau is composed of a base of ancient volcanic rocks, upon which rest, in ascending order, red sandstones and conglomerates of the Carboniferous age, Carboniferous limestone, variegated sandstones (Nubian sandstone) of Lower Cretaceous age, and Cretaceous limestones. The deeply cut ravines of the Moabite plateau owe their origin to the same subsidence, but their features, and those of the hills east and west of the lake, were greatly modified by the heavy rainfall in the Pliocene and Pleistocene periods. Terraces of lacustrine deposits at different levels indicate that in Pleistocene times the Jordan valley was occupied by a lake 200 miles long, which had the same surface level as the Mediterranean ; and that the water gradually subsided until, long before the dawn of history, the evaporation equalled the supply, and the lake assumed approximately its present level. The surface is liable to frequent fluctuations of level, which, though confined to narrow vertical limits, are sufficient to alter considerably the form and superficial extent of the lake. Such fluctuations are due to a succession of exceptionally dry or rainy seasons, to the greater or lesser activity of subaqueous springs, to landslips, to changes in the drainage, to the gradual silting up of the basin, and, possibly, to slight earth movements which escape detection. The annual rise and fall is estimated at from 6 to 10 feet, but there seems to be also prolonged periods of high and low level. The lines of driftwood and the marks on the rocks show the limits of rise which might occur under existing conditions, and a fall of 15 feet is quite possible after exceptional periods of dryness. Such a fall would dry up almost the whole of the lagoon south of el-Lisan, and effect great changes in the appearance of the lake. During the forty years 1860-1900 there was a gradual rise in the level of the surface, apparently coinciding in part with a succession of wet seasons, but accurate observations are wanting. A small island near the north end of the lake, which in 1858 was from 10 to 12 feet above the surface, and connected with the shore by a causeway, has been entirely submerged since 1892 ; and the track between Jebel Usdum and the lake has for several years been covered with water. Monthly measurements of the rise and fall of the lake, taken for the Palestine Exploration Fund during an exceptionally dry year, October 1900 to October 1901, showed a rise of 1 foot 3 inches up to 30th March 1901, and then a fall of 1 foot 9 inches to October. Thus the level of the lake was lowered 6 inches during the year. The asphalt or bitumen, so highly prized in ancient times, is supposed to be derived from subaqueous strata of bituminous limestone or marl, and to collect at the bottom of the lake until it is loosened by an earthquake and rises to the surface. The Arabs collect the bitumen which reaches the shore, and the salt of Jebel Usdum and of the Dead Sea has been carried to Jerusalem from the earliest times. But no systematic attempt has been made yet to turn the mineral wealth of the Dead Sea and its basin to account. The following analysis of water taken from the north end of the lake, not near the Jordan, in March 1885, when the level was high, was made by Dr Bernays :— Sp. gr. 1-1528 at 15-5 C. vjris. Calcium carbonate. . . 70-00 Calcium sulphate. . . 163 "39 Magnesium nitrate . . . 175 "01 Potassium chloride. . . 1089 "06 Sodium chloride . . . 5106-00 Calcium chloride . . . 594-46 Magnesium chloride. . . 7388-21 Magnesium bromide. . . 345"80 Iron and aluminium oxides. 10 "50 14,942-43 Organic matter, water of 317-57 crystallization and loss/ r due 15,260-00 j( SrainS tf ’ per gallon. S. III.— 50