THERMAL SPRINGS. 19D 



the funnel of the boiling spring, one -third of its diameter, and 

 surrounded by perpendicular walls, goes down to a depth of 

 75 feet. The temperature of the water which constantly 

 fills the basin is 180. At very regular intervals of one hour 

 and 20 or 30 minutes the thunder below proclaims the com- 

 mencement of the eruption. The jets of water, of 9 feet 

 in thickness, of which about three large ones follow one 

 another, attain a height of 100 and sometimes 1#0 feet. 

 The temperature of the water ascending in the funnel has 

 been found to be 2 60. 6 at a depth of 72 feet a little while 

 before the eruption, during the eruption 255.5, and imme- 

 diately after it 251.6 ; at the surface of the basin it is only 

 183 185. The Strokkr, which is also situated at the base 

 of the Bjarnafell, has a smaller mass of water than the 

 Geysir. The sinter margin of its basin is only a few inches 

 in height and breadth. The eruptions are more frequent 

 than in the Geysir, but do not announce themselves by sub- 

 terranean thunder. In the Strokkr the temperature during 

 the eruption is 235 239 at a depth of 42 feet, and almost 

 212 at the surface. -The eruptions of the intermittent boil- 

 ing springs, and the slight changes in the type of the pheno- 

 mena are perfectly independent of the eruptions of Hecla, and 

 were by no means disturbed by the latter in the years 1845 

 and 1846. 50 With his peculiar acuteness in observation and 

 discussion, Bun sen has refuted the earlier hypotheses regard- 

 ing the periodicity of the Geysir eruptions (subterranean 

 cauldrons, which, as steam-boilers, are filled sometimes with 

 vapours and sometimes with water). According to him the 

 eruptions are caused by a port ion of the column of water which 



50 Sartorius von Waltersbausen, PhysiscTi-geographische STcizze von 

 Island, mit besonderer Riicksicht auf vullcanische Erscheinungen, 1847, 

 s. 128 132 ; Bunsen and Descloiseaux, in the Comptes rendus des 

 Seances de VAcad. des Sciences, t. xxiii, 1846, p. 935 ; Bunsen, in the 

 Annalen der Chemie und Pharmacie, Bd. Ixii, 1847, s. 27 45. Lottiu 

 and Robert had already found that the temperature of the jet of water 

 in the Geysir diminishes from below upwards. Amongst the forty sili- 

 cious bubbling springs, which are situated in the vicinity of the Great 

 Geysir and Strokkr, one bears the name of the Little Geysir. Its jet 

 of water only rises 20 or 30 feet. The term boiling springs (Koch- 

 brunnen) is derived from the word Geysir, which is connected with the 

 Icelandic giosa (to boil). On the high land of Thibet also, according to 

 the report of Esoma de Koros, there is, nenr the Alpine lake Mapham 

 a Geysir, which rises to the height of 12 feet. 



