Coming to Petra from Eljy, on the east, the body of the regular mountain on that side is limestone, and higher than the red sandstone, where the tombs in Wadi Mousa are excavated. The cliffs at Petra are of _red sandstone_, which is soft and easily cut, causing the sculptures to decay quickly, unless where they may have been _protected_ from the weather. This formation extends far to the north and south, and rests on the lower masses of porphyry. The colour of the _sandstone_ rocks in Wadi Mousa is not a dull monotonous _red_, but a variety of bright hues, "from the deepest crimson," as Dr Robinson writes (vol. ii., p. 531), "to the softest pink; verging also sometimes to orange and yellow. These varying shades are often distinctly marked by waving lines, imparting to the surface of the rock a succession of brilliant and changing tints, like the hues of watered silk, and adding greatly to the imposing effect of the sculptured monuments." The site of Petra, in the high ravine, is called by the Arabs, Wadi _Mousa_; most likely corrupted from _Moseroth_, or _Mosera_ (Deut. x. 6), "where Aaron died and was buried." It is extremely interesting, and is well watered by a flowing stream--the _El Syk_ of Burckhardt. The _sandstone_ rocks, with their craggy and precipitous sides, have their summits resembling rounded peaks; peaks, probably owing to the softness of the stone, rounded by the effects of weather. The height of this _Wadi_ is estimated at near 2200 feet above the adjoining Wadi-el-Araba. To the west of Petra, Mount Hor, Gebel _Harun_ constitutes the loftiest point of this _sandstone_ tract. It stands out conspicuously, and is a _cone_ irregularly truncated with three rugged peaks, of which that to the NE. is the _highest_, and has upon it the Mahommetan _Wely_; or the tomb of _Aaron_, called _Neby Harun_. This peak rises to about 2700 feet above Wadi _Mousa_, or to 5300 feet above the sea.