ON PETRA, THE ROCK-HEWN CAPITAL OF IDUMMA. 147 
The formation of this remarkable valley is intimately con- 
nected with the geological history of Arabia Petraea and 
Palestine. Down to the close of the early Tertiary epoch, 
known as the Hocene, the whole of this region formed a part 
of the bed of the ocean; the only lands within a circuit of 
several hundred miles around being the summits of the Sinaitic 
Mountains, which probably rose above the surface in the form 
of an archipelago of islands. But during the succeeding 
Middle Tertiary epoch, known as the Miocene, all this was 
changed. The crust over the part of the globe bordering the 
Mediterranean of the present day, which for a lengthened 
period had been at rest, or was only slightly subsiding, gave 
way to the irresistible strain due to contraction, the result of the 
process of secular cooling. ‘The strata were bent, fractured, 
and displaced ; some portions relatively elevated, and thus con- 
verted into dry land, while others were more deeply depressed. 
In this way, and at this period, the regions of Northern Africa, 
Arabia, Palestine, and Syria were converted into land areas, 
and their outline, together with that of the adjoining seas, 
roughly defined. Amongst the leading lines of fracture and 
displacement (known technically as faults), one was produced 
of over-mastering influence in the formation of the physical 
features of the region now under description. ‘This fracture, 
known as “the Jordan-Arabah fault,’ has been traced at 
intervals from the head of the Gulf of Akabah northwards 
along the base of the Edomite and Moabite Mountains, and 
alone the line of the Jordan Valley to the western base of 
Hermon, and thence (recently by Dr. Carl Diener) into the 
Valley of Coele-Syria, a total distance of over three hundred 
miles ; how much further its influence is felt in the stratifica- 
tion is not at present known. LHverywhere on approaching 
this leading line of fracture the strata are displaced, having 
been elevated along the eastern, or lowered along the western, 
side. Adjoining this line, the depressions of the Arabah, the 
Jordan, the Litany, and the Orontes have been produced, 
partly by rain and river erosion, partly by actual displacement 
of the strata; while the table-lands of Edom, Moab, and of the 
Syrian Desert have been elevated along the Hastern side. 
Concurrently with the structural changes in the position of 
the strata, numerous valleys descending from the table-lands 
on either side began to be hollowed out by streams descending 
into the great Jordan-Arabah depression. Amongst these is 
the Wady Musa, or Valley of Petra. The stream which flows 
along this valley, generally as a gentle rivulet, fringed with 
oleanders, tamarisks, and reeds, takes its rise in springs, 
which break out at the base of the cretaceous limestone- 
