212 COSMOS. 



When Boussingault visited the Azufral cle Quindiu, thirty 

 years after me (1831), the temperature of the vapors which 

 he analyzed* had so greatly diminished as to fall below that 

 of the open air (71-6), namely to 66 68. The same 

 excellent observer saw the trachytic rock of the neighboring 

 volcano of Tolima, breaking through the mica-schist, in the 

 Quebrada de Aguas calientes: just as I have very distinctly 

 seen the equally eruptive, black trachyte of the volcano of 

 Tunguragua covering a greenish mica-schist containing gar- 

 net near the rope bridge of Felipe. As sulphur has hither- 

 to been found in Europe, not in the primitive rocks, as they 

 were formerly called, but only in the tertiary limestone, in 

 gypsum, in conglomerates, and in true volcanic rocks, its 

 occurrence in the Azufral de Quindiu (41 N. lat.) is the 

 more remarkable, as it is repeated to the south of the equa- 

 tor between Quito and Cuenca, on the northern slope of the 

 Paramo del Assuay. In the Azufral of the Cerro Cuello 

 (2 13' S. lat.), again in mica-schist, at an elevation of 

 7980 feet, I met with a vast bed of quartz,f in which the 

 sulphur is disseminated abundantly in scattered masses. At 

 the time of my journey the fragments of sulphur measured 

 only 6 8 inches, but they were formerly found of as much 

 as 3 4 feet in diameter. Even a naphtha spring rises vis- 

 ibly from mica-schist in the sea-bottom in the Gulf of Cari- 

 aco, near Cumana. There the naphtha gives a yellow color 

 to the surface of the sea to a distance of more than a thou- 

 sand feet, and I found that its odor was diffused as far as the 

 interior of the peninsula of Araya.f 



* Humboldt, Essai Geognostique stir Je Gisement des Roches dans les 

 deux Hemispheres, 1823, p. 76; Boussingault, in the Annaks de Cliemie 

 et de Physique, t. Hi., 1838, p. 11. 



f With regard to the elevation of Alausi (near Ticsan), on the Cerro 

 Cuello, see the " Nivellement barometrique, No. 206," in my Observ. 

 Astron., vol. i., p. 311. 



| " The existence of a naphtha spring issuing at the bottom of the 

 sea from, a mica-schist, rich in garnets, and diffusing, according to 

 the expression of the historian of the Conquista, Oviedo, a " resinous, 

 aromatic, and medicinal liquid," is an extremely remarkable fact. 

 All those hitherto known belong to secondary mountains; and this 

 mode of stratification appeared to favor the idea that all the mineral 

 bitumens (Hatchett, Transact. Linncean Society, 1798, p. 129) were due 

 to the destruction of vegetable and animal matters, or to the ignition 

 of coal. The phenomenon of the Gulf of Cariaco acquires fresh im- 

 portance, if we bear in mind that the same so-called primitive stra- 

 tum contains subterranean fires, that the odor of petroleum is ex- 

 perienced from time to time at the edge of ignited craters (for ex- 

 ample, in the eruption of Vesuvius in 1805, when the volcano threw 



