84 WALKS AND TALKS. 



parts of the world. Some of those of New Zealand present 

 close resemblances to the Mammoth Hot Springs of Gardiner's 

 river. Geysers occur also, in New Zealand ; but the most 

 celebrated is the Great Geyser of Iceland. To impart a con- 

 ception of its behavior in eruption, the following description 

 by S. Baring Gould is cited: "Five strokes under ground 

 were the signal, then an overflow, wetting every side of the 

 mound. Presently a dome of water rose in the centre of the 

 basin and fell again, immediately to be followed by a fresh 

 bell, which sprang into the air full forty feet high, accompa- 

 nied by a roaring burst of steam. Instantly, the fountain 

 began to play with the utmost violence ; a column rushed up 

 to the height of ninety or one hundred feet, against the gray 

 night sky, with mighty volume of white steam cloud rolling 

 about it, and swept off by the breeze to fall in torrents of hot 

 rain. Jets and lines of water tore their "way through the 

 cloud, or leaped high above its domed mass. The earth 

 trembled and throbbed during the explosion, then the column 

 sank, started up again, dropped once more, and seemed to be 

 sucked back into the earth." Pen and Pencil Sketches of Faroe 

 and Iceland. 



No one can contemplate the phenomena of a geyser or hot 

 spring without feeling a conviction that heat is the essential 

 condition. Somewhere within the earth is a repository of heat 

 sufficient to warm, or even to boil, the water which rises to 

 the surface. Strata whose outcropping edges appear at the 

 surface, receive rain-water and convey it along the dip to un- 

 known depths. In the geyser, some concurrent conditions 

 must exist. I* is admitted that the water rises through a 

 tube, and that in its lower part a temperature exists sufficient 

 to boil water under the pressure there existing. But details 

 of the mechanism are not unanimously agreed upon. They 

 are probably somewhat as follows : Water accumulates in the 

 geyser pipe upon the steam formed in the lower part by the 

 bottom temperature. The steam, for a time, is subjected to 

 compression, and the compression increases with the continued 

 development of steam and accumulation of water. Finally, 



