On the plain to the north of the Jebel el-Abyaz also, I found curdles of porphyritic trap, and parallel trap-dykes, cutting the courses of large-grained grey granite: as many as three outcrops of the former appeared within fourteen yards. This convinced me that the whole of the solid square, thirty kilometres (six by five), where the quartz emerges, is underlaid by veins and veinlets of the same rock. Moreover, I then suspected, and afterwards ascertained, that the quartz of the Jibál el-Bayzá, as the Bedawin call this section, is not a local peculiarity. It everywhere bursts, not only the plain between the sea and the coast-range, but the two parallels of mountain which confine it on the east. In fact, throughout our northern march the Arabs, understanding that its object was "Marú," the generic name for quartz,[EN#23] brought us loads of specimens from every direction. Nothing is easier than to work the purely superficial part. A few barrels of gunpowder and half a dozen English miners, with pick and crowbar, suffice. Even our dawdling, feckless quarrymen easily broke and "spelled" for camel loading some six tons in one day. Our short se'nnight was not wasted; yet I had an uncomfortable feeling that the complication of the country called for an exploration of months and not hours. Every day some novelty appeared. The watercourses of the Gháts or coast-range were streaked with a heavy, metallic, quartzose black sand which M. Marie vainly attempted to analyze. We afterwards found it in almost every Wady, and running north as far as El-'Akabah; whilst, with few exceptions, all our washings of red earth, chloritic sand, and bruised stone, yielded it and it only. It is apparently the produce of granite and syenite, and it abounds in African Egypt. I was in hopes that tungsten and titaniferous iron would make it valuable for cutlery as the black sand of New Zealand. Experiments in the Citadel, Cairo, produced nothing save magnetic iron with a trace of lead. But according to Colonel Ross, the learned author of "Pyrology, or Fire Chemistry,"[EN#24] it is iserine or magnetic ilmenite, titaniferous iron-sand, containing eighty-eight per cent. of iron (oxides and sesquioxides), with eleven per cent. of titanic acid.