200 REACTION OF THE INTERIOR OF THE EARTH 



greatly diminished, temperature suiting those crea- 

 tures extremely well. In the extreme north of India 

 (lat. 30 52'), the very hot spring of Jumnotri rises 

 out of granite, at an elevation of 10,850 feet above 

 the sea-level, with a temperature of 194 Fahr., being 

 nearly the boiling point of water under the atmospheric 

 pressure corresponding to that altitude. ( 273 ) 



Among intermitting hot springs, the boiling fountains 

 of Iceland, and among these especially the Great Greysir 

 and the Strokr, have deservedly acquired the most 

 celebrity. In both, according to the excellent recent 

 researches of Bunsen, Sartorius von Waltershausen, and 

 Descloiseaux, the temperature in the jets of water de- 

 creases from below upward with remarkable rapidity. 

 The Greysir has a truncated cone, about 26 or 30 feet high, 

 formed of horizontal strata of silicious concretion. In 

 this cone there is a shallow depression about 55 or 56 

 feet broad, in the middle of which a funnel about 1 8 feet 

 in diameter descends to a depth of 75 feet. The tempe- 

 rature of the water, which always fills the basin, is nearly 

 180 Fahr. At very regular intervals of about 80 or 90 

 minutes, subterranean thunder announces the beginning 

 of the eruption. Columns of water nine or ten feet dia- 

 meter, of which about three large ones follow each other 

 in immediate succession, shoot upwards to the height of 

 more than a hundred, sometimes to even nearly a hun- 

 dred and fifty feet. The temperature of the water which 

 rises in the funnel has been measured at a depth 

 of 72-i- feet, and found, a short time before the eruption, 

 260-6 ; during the eruption, 255'6 ; and immediately 

 after it 251*6 At the surface of the basin it was 

 only from 183 to 185. The Strokr, which is also 



