AND RIVERS OF INDIA AND EGYPT, ETC. ISf 



source at an elevation having a mean temperature lower than that of the plain where 

 the water appears on the surface. 



2nd. The temperature of strongly saline and sulphureous springs is, on the average, 

 higher than those of pure water. 



3rd. Both saline and cold springs are seen to occur within a few feet from thermal 

 and freshwater springs; a fact to be ascribed probably to their rising through 

 different seams of the subjacent stmta (often highly inclined), and to the different 

 depths and heights from which the supply of water is derived. 



4th. The temperature of wells, particularly those with a small area, much used for 

 purposes of irrigation, is thereby artificially increased. 



5th. The temperature of shallow exposed wells, springs and rivers, especially such 

 as have sandy beds, is subject to great diurnal fluctuation, conforming, though to a 

 less extent, to that of the superincumbent atmosphere. The surface water of deep 

 wells partakes of this fluctuation, to a depth varying according to the transparency 

 of the water, extent of surface, degree of exposure, and clearness of the sky. In 

 muddy water the surface is heated to a greater extent, but a foot or two deep is less 

 affected by the calorific action of the solar rays than clear water. 



The transparent water of a large well at Bellary, lat. 15° 5' N. and long. 76° 59' E., 

 situate on a table-land elevated 1600 feet above the sea's level, and containing sixteen 

 feet of water, I found, at the depth of nine feet from the surface, to vary but one 

 degree during the day, from sunrise to sunset, and this in several hundred experi- 

 ments. The minimum, 79°*5, took place a little after sunrise, and the maximum, 80°-5, 

 at 3 P.M. following those of the air. The diurnal variation of the water an inch below 

 the surface amounted to 12°. During the commencement of the dry weather, as the 

 heat increased, the water gradually decreased, and the diurnal fluctuations became 

 greater, and increased at a greater rate than that of the decrease of the water. 



Thermal Springs. — The thermal springs, both of India, the peninsula of Sinai and 

 Egypt, are, with few exceptions, either mineral or gaseous. Those near the shores 

 of the Red Sea are sulphureous ; and strictly speaking, perhaps, should not be classed 

 as thermal springs, from the great probability of their being connected with the vol- 

 canic belt that passes under the bed of the Red Sea, and bursting up from its watery 

 fetters appears in the semi-dormant volcano of Gebel Teer, and in the lavas of Aden, 

 beyond the straits of Babel-Mandel. The highest known temperature of the thermal 

 springs is 102°, viz. that of El Kasr in the Oasis of Dakhleh ; in the peninsula of Sinai, 

 91°6, that of the Hum mam Musa, hot-baths of Moses (Wells of Elim ?) near Tor, It 

 is probable, from reports given me by the Arabs, that the Humm^m Pharaon, hot-baths 

 of Pharaoh, about eighty-five miles northerly from Tor, are of higher temperature. 

 The maximum attained by the thermal springs of India is 1 94° at Jumnotri in North 

 Hindostan (lat. 30° 52' N.) ; a temperature almost equivalent, at that elevation — 

 10849 feet above the sea's level — to the boiling point of water, and 18° higher than that 

 of the hottest known thermal spring of Europe unconnected with present active vol- 



