148 PROFESSOR HULL, LLD., F.R.S. 
terrace forming the margin of the great Arabian plateau, 
which here rises to a level of about 5,000 feet above the sea, 
and, having cut its channel deep into the underlying “‘ Nubian 
sandstone,” ultimately emerges on the Arabah plain, and 
flowing northwards, unites with the River Jeib a few miles to 
the south of the Dead Sea, into which the waters pass.” The 
streams of Edom, generally tiny and feeble throughout the 
greater part of the year, descend with great force and impe- 
tuosity when replenished by the thunderstorms which burst, 
from time to time, upon the mountains during the three or 
four winter months of the year. From this cause they have 
cut down their channels to extraordinary depths, especially 
when they traverse the soft sandstone of which the central 
parts of the range of Mount Seir are mainly composed, and 
which breaks off in grand precipices along the master-joints 
and faults which traverse the rocks in various directions. 
This sandstone rock (known as “‘ The Nubian Sandstone of 
Russegger ”’), two or three thousand feet in thickness, with 
its base on very ancient volcanic crystalline rocks, and sur- 
mounted by the white cretaceous limestone lining the sides of 
the valley in a series of noble cliffs, vertical walls, or succes- 
sive terraces, afforded an admirable opportunity for the 
construction of a city, unique because cut out of the living 
rock itself. The stone, compact, moderately hard and uniform 
in texture, coloured moreover with ever-varying shades of 
orange, red, and purple, disposed in bands and wavy folds, 
which give the surface the appearance of some gorgeous Hastern 
robe, formed a suitable material for the skilled masons and 
architects of the period. As we gaze on those noble specimens 
of a bygone art—sometimes clinging, as it were, to the sides 
of the precipitous valley—we ask ourselves what was the 
modus operandi adopted in their construction? Did the 
architects commence from below or from above, in the work 
of hewing and shaping the rock-faces standing up before 
them, or frowning down upon them so forbiddingly? - I 
venture to reply, “from above”’; first, and chiefly, for greater 
security against accidents from falling blocks ; and, secondly, 
because it was always possible to add to the vertical height 
of the building, when this was required, simply by cutting 
down deeper below, while from the natural slope of the face 
the builders were limited in an upward direction. Above all 
things, it was necessary that the crowning portion of the 
fabric should be complete and entire, and this could only be 
easily accomplished by commencing at the top and working 
downwards. In a few cases the holes for the insertion of 
the timber scaffolding are still visible. We may, therefore, 
