Besides the springs at the inhabited spots above described, and those used for irrigated lands more or less near to them, there are numerous outlying springs, which, while not serving for irrigation, are important as localities where water may be obtained. The chief of these are Ain Gelid, on the road from Minia and Samalut, 3½ kilometres south-east of Harra; Ain Haswi, 9½ kilometres due south of Harra, to which two roads from the east scarp converge; Ain Beled, 7 kilometres west of Bawitti; and Ain Khaman, half-way between Ain el Haiss and the south point of the oasis. The water at Ain Khaman is said to be bitter and the spring is apparently frequently sanded-up and difficult to find, so that travellers to Farafra should take in their supplies at Ain el Haiss. * * * * * [Footnote 31: _Recensement général de l’Égypte_, tome III, 1896.] [Footnote 32: Includes about 50 inhabitants of the hamlet of Harra.] [Footnote 33: A bottle of the water tightly corked burst shortly afterwards by gaseous pressure; the bottle having been filled at the bottom of the well doubtless accounts for this, the pressure due to the head having caused solution of the gas to a greater extent than could be supported at the surface. The evolved gas was at first suspected to be methane, as there is frequently a great deal of decaying vegetable matter in the mouths of the wells; but it extinguished a taper, and, moreover, the water runs too rapidly for any accumulation of gaseous decomposition-products to take place.] [Footnote 34: In Dakhla and Kharga Oases there are only seven and a half and eight trees respectively per inhabitant.] CHAPTER V. * * * * * GEOLOGY OF THE OASIS. [Sidenote: Previous geological work.] The earliest geological observations made in Baharia Oasis appear to have been those of Cailliaud,[35] who visited the district in 1820, and recorded the occurrence of volcanic rocks within the depression. In 1874 the celebrated Rohlfs Expedition was organised, and in that and the succeeding year traversed large portions of the Libyan Desert. The work of this Expedition, forms indeed, the basis of our knowledge of the geology of Egypt generally. The eminent geologist and palæontologist of that Expedition, Karl A. Zittel, did not, however, visit Baharia, and the only information with regard to the geology of this oasis was derived from specimens collected by Prof. Ascherson. After examining these, Zittel stated[36] that the floor of the oasis consisted of sandstones, marls, etc., presenting a considerable resemblance to the lower part of the Overwegi stage;[37] but concluded, that as they were succeeded at a very short interval by Nummulitic Limestone, precluding the possibility of the higher Cretaceous beds, except in a very attenuated form, they must be of Tertiary age.