834 THE POPULAR SCIENCE MONTHLY.
tant period sink below the level of the bottom of the channel that con- nects the Karabogaz with it.
The character of the Dead Sea is still in question. M. Lartet, of Toulouse, who was connected with the expedition of the Due de Luynes in 1866, fully recognizes the close analogy of its waters with the mother- waters that are left from the evaporation of the waters of normal seas ; but he believes that its waters owe their quality to ther- mal springs, and that the sea never could have been in communication with the Mediterranean or the Red Sea. He supports his view by the assumed absence of certain substances common to sea-waters from its waters ; but, as I have found these substances by analysis in Dead Sea waters, I consider the argument resting upon that ground invalid. M. Lortet, of Lyons, has recently made a discovery that indicates that this lake once formed part of a normal sea. He has found near the Lake of Tiberias a plateau covered with gravel and rounded pebbles, situated at the exact level of the Mediterranean Sea. If the body of water that washed these gravels and pebbles once occupied the valley of the Jordan and the Dead Sea, then there once existed here a gulf like that of Karabogaz. Separated from the oceans by some accident, it has dried up ; its less soluble salts have been gradually deposited in the shallower parts of the basin and constitute the saline masses which are now found in the region products of the sea instead of being the causes of its saltness ; and the deliquescent salts have become concen- trated, as in modern estuaries, into the still liquid part that constitutes a mother-water fully comparable in all respects to the mother-waters of the salt-marshes of the south of France.
I conclude with a summary of the principal facts to which I have directed attention.
At the moment when the first crust of consolidation began to form around our globe, chlorine and sulphur, now existing in combinations, were in the atmosphere. When the temperature had sufficiently dimin- ished, these two bodies, reacting on the exterior crust of our globe, formed, at intervals otherwise extremely distant, combinations (sul- phates and chlorides) by uniting with the metals that existed and still exist in the rocks constituting that first envelope. These metals, combined almost exclusively with sulphur and chlorine, are precisely the ones (lithium, potassium, sodium, magnesium, calcium) that still mineralize the waters of the seas. The salts thus formed, dissolved in the waters from the most ancient age of the aqueous period of our planet, have, then, a wholly exterior origin. Later, under the influence of causes often extremely insignificant in themselves, parts of these seas have been isolated from the oceans ; they have evaporated, and, according to the degree of completeness in which concentration has been effected, they have deposited salt-beds sometimes of a complex enough nature, but which have uniformly presented the typical char- acter that they begin with deposits of gypsum. Such is the origin of