

kwi 





" ( 



N 







** 



l 



ml 



^ 



8 



h-. 



ore 



w 



- 



■ 



tt 



rd.be 



es.as 



liters 



old 



s 







tr l 







Ch. XVII.] 



GEYSERS OF ICELAND. 



409 



sinter mixed with clay, including grass, ferns, and reeds, in 

 different states of petrifaction. In some instances, alumina, 

 which is likewise deposited from the hot waters, is the mi- 

 neralising material. Branches of the same ferns which now 

 flourish in the island are found completely petrified, pre- 

 serving the same appearance as when vegetating, except that 

 they acquire an ash-grey colour. Fragments of wood, and 

 an entire stratum from three to five feet thick, composed of 

 reeds now common in the island, have become completely 

 mineralised. 



The most abundant variety of siliceous sinter occurs in 

 layers, from a quarter to half an inch in thickness, accumu- 

 lated on each other often to the height of a foot and upwards, 

 and constituting parallel, and for the most part horizontal, 

 strata many yards in extent. This sinter has often a beau- 

 tiful semi-opalescent lustre. A recent breccia is also in the 

 act of forming, composed of obsidian, pumice, and scoriae, 

 cemented by siliceous sinter."* 



'/ 



— The origin of the Icelandic Geysers, 



intermittent 



XXXIII 



me 



t 



The 



action is treated of. I shall 

 illustrating the deposition of 

 circular reservoirs into which the geysers fall, are lined in 

 the interior with a variety of opal, and round the edges with 

 sinter. The plants incrusted with the latter substance have 

 much the same appearance as those incrusted with calcareous 

 tufa in our own country. They consist of various grasses, the 

 horse-tail (Equisetum), and leaves of the birch-tree, which 

 are the most common of all, though no trees of this species 

 now exist in the surrounding country. The petrified stems 



wood.t 



much resembling 



By analysis of the water, Mr. Faraday has ascertained 



the alkali, soda. He 



promoted 



* Dr. Webster on the Hot Springs of Chap. XXXIII. 

 Furnas, Ed. Phil. Journ. vol. vi. p. 306. 

 bee a cut of the Icelandic geyser, 



\ M. Robert, Bulletin de la Soc. 

 Geol. de France, torn. vii. p. 11. 



•r 



