218 COSMOS. 



from the fissures of the earth not only occur in the distncta 

 of still burning or long-extinguished volcanoes, but they may 

 likewise be observed occasionally in districts where neither 

 trachyte nor any other volcanic rocks are exposed on the 

 earth's surface. In the chain of Quindiu I have seen sul- 

 phur deposited in mica slate from warm sulphurous vapor 

 at an elevation of 6832 feet* above the level of the sea, 

 while the same species of rock, which was formerly regarded 

 as primitive, contains, in the Cerro Cuello, near Tiscan, south 

 of Quito, an immense deposit of sulphur imbedded in pure 

 quartz. 



Exhalations of carbonic acid {mofettes) are even in our days 

 to be considered as the most important of all gaseous emana- 

 tions, with respect to their number and the amount of their 

 effusion. We see in Germany, in the deep valleys of the 

 Eifel, in the neighborhood of the Lake of Laach,! in the 

 crater-like valley of the Wehr and in Western Bohemia, ex- 

 halations of carbonic acid gas manifest themselves as the last 

 efforts of volcanic activity in or near the foci of an earlier 

 World. In those earlier periods, when a higher terrestrial 

 temperature existed, and when a great number of fissures 

 still remained unfilled, the processes we have described acted 

 more powerfully, and carbonic acid and hot steam were mixed 

 in larger quantities in the atmosphere, from whence it follows, 

 as Adolph Brongniart has ingeniously shown,$ that the primi 

 tive vegetable world must have exhibited almost every where, 

 and independently of geographical position, the most luxurious 

 abundance and the fullest development of organism. In these 

 constantly warm and damp atmospheric strata, saturated with 



* Humboldt, Recueil d'Observ. Astronomiques, t. i., p. 311 {Nivelle 

 ment Barom6trique de la Cordillere des Andes, No. 206). 



t [The Lake of Laach, in the district of the Eifel, is an expanse of 

 water two miles in circumference. The thickness of the vegetation on 

 the sides of its crater-like basin renders it difficult to discover the nature 

 of the subjacent rock, but it is probably composed of black cellular 

 augitic lava. The sides of the cralgr present numerous loose masses, 

 which appear to have been ejected, and consist of glassy feldspar, ice- 

 spar, sodaHte, hauyne, spinellane, and leucite. The resemblance be- 

 tween these products and the masses formerly ejected from Vesuvius is 

 most remarkable. (Daubeney On Volcanoes, p. 81.) Dr. Hibbert re- 

 gards the Lake of Laach as formed in the first instance by a crack 

 caused by the cooling of the crust of the earth, which was widened 

 afterward into a circular cavity by the expansive force of elastic vapors. 

 See History of the pxtinct Volcanoes of the Basin of Neuwied, 1832.3 

 ^Tr. 



t Adolph Brongniart, in the Annalss des Sciences Naturelles, t. xv.. 

 p. 225. 



