At the head of the Wady el-Maka'dah we halted six days (December 24--30); this delay gave us time to correct the misapprehensions of our flying visit. The height of the Jebel el-Abyaz, whose colour makes it conspicuous even from the offing when sailing along the coast, was found to be 350 (not 600) feet above the plain. The Grand Filon, which a mauvais plaisant of a reviewer called the "Grand Filou," forms a "nick" near the hill-top, but does not bifurcate in the interior. The fork is of heavy greenish porphyritic trap, also probably titaniferous iron, with a trace of silver,[EN#22] where it meets the quartz and the granite. Standing upon the "old man" with which we had marked the top, I counted five several dykes or outcrops to the east (inland), and one to the west, cutting the prism from north to south; the superficial matter of these injections showed concentric circles like ropy lava. The shape of the block is a saddleback, and the lay is west-east, curving round to the south. The formation is of the coarse grey granite general throughout the Province, and it is dyked and sliced by quartz veins of the amorphous type, crystals being everywhere rare in Midian (?) The filons and filets, varying in thickness from eight metres to a few lines, are so numerous that the whole surface appears to be quartz tarnished by atmospheric corrosion to a dull, pale-grey yellow; while the fracture, sharp and cutting as glass or obsidian, is dazzling and milk-white, except where spotted with pyrites--copper or iron. The neptunian quartz, again, has everywhere been cut by plutonic injections of porphyritic trap, veins averaging perhaps two metres, with a north-south strike, and a dip of 75 degrees (mag.) west. If the capping were removed, the sub-surface would, doubtless, bear the semblance of a honeycomb. The Jebel el-Abyaz is apparently the centre of the quartzose outcrop in North Midian (Madyan Proper). We judged that it had been a little worked by the ancients, from the rents in the reef that outcrops, like a castle-wall, on the northern and eastern flanks. There are still traces of roads or paths; while heaps, strews, and scatters of stone, handbroken and not showing the natural fracture, whiten like snow the lower slopes of the western hill base. They contrast curiously with the hard felspathic stones and the lithographic calcaires bearing the moss-like impress of metallic dendrites; these occur in many parts near the seaboard, and we found them in Southern as well as in Northern Midian. The conspicuous hill is one of four mamelons thus disposed in bird's-eye view; the dotted line shows the supposed direction of the lode in the Jibál el-Bayzá, the collective name.