Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/102

 the entire length of the Nasb valley, is strewn with masses of a hard black haematite, in angular blocks with sand-scratched surfaces, having a somewhat scoriaceous look. This appears to have been confused by travellers at different times with the actual copper-slags that exist in the same valley. Blue and green carbonate of copper, and a little calamine, are also found in the sandstones on the same horizon.

Old Mines. — Several small pits have been opened upon the iron and manganese bed, both at Nasb and on the top of the adjoining table-land. As far as can be made out from Arab accounts, none of these are of any great age, the most important dating from about sixty years back. Several camel-loads of pyrolusite are said to have been taken from a pit on the hill, and sent to Cairo as an experiment, the general belief being that it was sold for use in colouring the eyelids (kohll) instead of galena. If this was the purpose to which it was really applied, we can easily understand why the experiment was never repeated. On the western side of the Nasb Valley there are indications of old workings, besides modern levels driven a short distance into the side of the hill ; but their exact nature is not quite clear, as they have become choked up with rubbish, partly from the fall of the roof, but more from the sand and wash of the valley brought down by the rains.

At Wady Khalig, a tributary of Wady Baba, about four miles below Nasb, the iron and manganese bed has been extensively excavated by the old miners. Here it occurs under the form of a soft schistose white marl, variegated with green and red patches, and contains small strings of earthy-brown iron-ore, with a little blue and green carbonate of copper, and the smallest possible spots of copper-glance or perhaps indigo copper-ore. The old workings extend about 120 yards along the face of the hill. Near the surface the roof has fallen in many places, leaving a large irregular cavern, with several openings to the day. Deeper under the hill, where the rock has been better protected from the weather, the height of the excavation is about 5 feet, and the whole of the ground has been removed, with the exception of a few small pillars at distances of about 50 feet apart. The walls and pillars are covered with small chisel- or gad-marks, apparently made with a tool about 3/4 or 7/8 of an inch in breadth. The distance to which the workings extend from the face of the hill is about 40 yards ; but this cannot be determined exactly, as there is a considerable deposit of muddy sand on the floor, washed in by the rains (the bed having been followed on the dip), which has no doubt completely filled up the lowest part of the mine. In some places the roof is supported by stone and mortar walls ; but these are probably of newer date, having been put up to render the cavern secure for the purpose of a dwelling or a store-house.

There are no inscriptions or any other guide to the probable date of these workings; but it is evident, from the extraordinarily poor character of the ore, that they must belong to a very early period, when metals were of nearly uniform value, owing to their produc-