2$6 Medicinal Mineral Water at Helwdn. 



" The lowest strata of the Mokattam run parallel to the 

 valley of the Nile as far as Massara. These lower strata 

 are capped by layers of limestone, calcareous grit, and ar- 

 gillaceous sandstone containing iron, separated from each 

 other by sands, marls, and bituminous shales, containing, all 

 of them, sulphate of lime. Near Helwan, the argillaceous 

 layers and softer limestones prevail. The summit-level of 

 the desert between the Nile and the Red Sea is about thirty 

 miles to the N.E. of Helwan. It frequently rains there in 

 winter, and torrents precipitate themselves into the Nile by 

 channels having beds of clay covered by sand. A large por- 

 tion of the water may be detained in basins, natural and ar- 

 tificial, and from thence passing between the layers of im- 

 pervious clays, through ferruginous and sulphurous shales 

 and sands containing also crystallized gypsum, come out at 

 Helwan, and at several other places above the Helwan springs 

 on this side of the Mokattam, and at Aine el Moussa on the 

 Red Sea, where there is a warm spring, similar in quality to 

 that at Helwan. The elevation of the springs above the val- 

 ley is about 40 feet. From the highest level of the Nile in- 

 undations, the ground rises very gently, and for the first mile 

 is sand mixed with clay ; this is succeeded by a zone of flat 

 ground, covered at first with a slight crust of saline clay, the 

 salt increasing in quantity towards the springs. The plain 

 ends at the foot of a very slightly elevated plateau of loose 

 dry shales and marls, running nearly horizontally from north 

 to south. M. Hekekyan Bey adds, — ■ I think there is only 

 one spring. The temperature of the water felt warm to our 

 hands after an exposure of several hours to the burning rays 

 of an Egyptian sun in the month of June. Sulphurous hy- 

 drogen gas rises from the limpid water of the spring. It is 

 rather bitter to the taste, and there is something peculiarly 

 unctuous to the touch in its deposits, which I may compare 

 to the white of a raw egg. I perceived no thin plates on the 

 water. The supply is considerable, for it is made to water 

 about three or four acres of sedge, used for matting. I pre- 

 sume that the water of the springs, having filled up the line 

 of hollows that serve as a reservoir for it, running over, oozes 

 down in a westerly direction through a surface-layer of sand 



