ed sandstone, at other
times, on the granite and other crystalline rocks of great geological
antiquity. In addition to the sheets of basalt, numerous crater-cones
rise from the basaltic platform at a level of 5000 feet above the sea,
and two volcanic mountains, rising far to the west of the principal
range, called respectively Harrat Jeheyma and H. Rodwa, almost overlook
the coast of the Red Sea.[10]

(_f._) _Age of the Volcanic Eruptions._--It is very clear that the first
eruptions, producing the great basaltic sheets of Moab and Arabia,
occurred after the principal features of the country had been developed.
The depression of the Jordan-Arabah valley, the elevation of the eastern
side of this valley along the great fault line, and the channels of the
principal tributary streams, such as those of the Yarmuk and Zerka Main,
all these had been eroded out before they were invaded by the molten
streams of lava. Now, as these physical features were developed and
sculptured out during the Miocene period, as I have elsewhere shown to
be the case,[11] we may with great probability refer the volcanic
eruptions to the geological epoch following--namely, the Pliocene. How
far downwards towards the historic period the eruptions continued is not
so certain. Dr. Daubeny, quoting several passages from the Old Testament
prophets,[12] says it might be inferred that volcanoes were in activity
even so late as to admit of their being included within the limits of
authentic history. The poetic language and imagery used in these
passages by the prophets certainly lends a probability to this view, but
nothing more. On the other hand, these regions have suffered through
many centuries from the secondary effects of seismic action and
subterranean forces, and earthquake shocks have laid in ruins the great
temples and palaces of Palmyra, Baalbec, and other cities of antiquity.
The same uncertainty regarding the time at which volcanic action died
out, with reference to the appearance of man on the scene, hangs over
the region of Arabia and Syria, as we have seen to be the case in
reference to the extinct volcanoes of Auvergne, the Eifel, and the Lower
Rhine. In all these cases the commencement and close of eruptive action
appear to have been very much about the same period--namely, the Miocene
period on the one hand, and that at which man entered upon the scene on
the other; but in the case of Syria and Western Palestine, the close of
the volcani