7 



I \--* 



:n 



ATE. 



rr 



THE 



OF 



AM) 



APirr- 



I > 



itit5:r 



'^ Li 



vi^ 



AlolUlt 



the 



ID. 





1 



train 



5t<; 



I 



The 



J 



{li 



:-''l 





linto 



tli?5 



I 





re 



Ch. XXXIIL] 



GEYSERS OF ICELAND. 



215 



propelled upwards, even to the smmnit of cones 3 miles in 



heiorlit.* 



/ 



— The extent to which porous rocks are 



percolated by rain-water to great depths in almost every 

 region, however far from the sea, has been alluded to in our 

 chapter on springs (Vol. I. p. 387) ; and as there is no doubt 

 that ordinary steam plays a prominent part in volcanic 



may 



to 



consider attentively a case in which we know it to be exclusively 



moving" 



These intermittent hot springs occur in a district situated in 

 the south-western division of Iceland, where nearly 100 of 



miles 



That 



the water is of atmosx)heric origin, derived from rain and 

 melted snow, is proved, says Professor Bunsen, by the nitrogen 



them either pure or mixed 



may 



Mount Hecla 



volcano beinsr seen from 



tliis district the 



rushing of water is 



than 30 miles. In 

 sometimes heard in chasms beneath the surface ; for here^ as 

 on Etna, rivers flow in subterranean channels through the 

 porous and cavernous lavas. 



mor 



some 



increased or diminished in violence and volume, or entirely 

 ceased, or that new ones have made their appearance — changes 

 which may be explained by the opening of new rents and the 

 closing of pre-existing fissures. 



Few of the Geysers play longer than 5 or 6 minutes at 



a time, although sometimes half an hour, 

 between their eruptions are for the most i3ar 



The intervals 



J 



summit 



of a circular mound composed of siliceous incrustations de- 

 posited from the spray of its waters. The 



diamet 



basin, in one direction, is 56 feet, and 46 in another. (See 

 fig. 129.) . ■ 



In the centre is a pipe 78 feet in perpendicular depth. 



* Geologj of American Exjploring Expedition, p. 369 



«4 



