CHILIAN VOLCANOES, ACTIVE AND EXTINCT. 89 



vapors consist chiefly of carbonic acid, sulphur compounds, and -water. 

 The present solid products do not differ greatly in composition from 

 the trachytes of the past. Audesite, or a feldspathic mineral very 

 nearly like it, is an important constituent of the porphyritic lavas of 

 both active and quiet volcanoes. Olivine is found in the older and in 

 the more recent lavas of Descobezado, Antuco, and Osorno, as well as 

 in those of Juan Fernandez, and very probably in the liquid outflows 

 of all the other craters. Other lavas occur, among them obsidian, 

 pearl-stone, pitch-stone, and pumice, the last being quite abundant in 

 the Cordilleras of Talca and Chilian. Lapilli cover the eastern flank 

 of Osorno to a depth of about sixteen feet, and through it rose as late 

 as 1851 the great, strong-limbed trunks of dead trees, whose thickness 

 indicated an age of about one hundred and fifty years, while it had 

 been about fifty years since the last eruption of the mountain. But it 

 was a laborious task to trace the lava-stream under the flourishing new 

 growth that had taken root in the weathered surface and in the crev- 

 ices of the hard deposit. 



Of the still active volcanoes, we may say that Atacama emitted 

 smoke after the earthquake of May, 1877. The group of San Jose 

 was active in 1833, threw rocks into the valley of Pinquenes in 1843, 

 and has been again active since the 2d of March, 1881. Numerous 

 crater-openings, with ancient lava-flows, are found in the same region. 

 Tinguiririca, to the south of this region, consists almost wholly of 

 trachyte, and has several solfataras about five thousand feet below its 

 summit, whence issue vapors having a temperature of 194° ; its thick 

 deposit of sulphur has caused it to be given the name of Morro de 

 Azufre, or Sulphur Mountain. More important still is the volcano of 

 Petesoa, at the outbreak of which, on the 3d of December, 1762, the 

 district was desolated with lava and ashes, and the Rio Lontue was 

 dammed up for ten days. Its last eruption, in February, 1837, was 

 followed by destructive floods in the lower-lying regions, caused by 

 the sudden melting and precipitation of the snows from its summit. 

 An immense horizontal ice-cap now lies in the crater, whence rise ver- 

 tically isolated columns of smoke that can be seen from a considerable 

 distance. Beyond this is the volcanic center of Descobezado, in the 

 southern part of which a solfatara opened in 1847 that kept the dis- 

 trict trembling for many years. 



The present region of active commotion begins at 36° 50' with the 

 volcano of Chilian. A new crater opened northeast of the principal 

 peak of this mountain on the 2d of August, 1861, the flow from which 

 melted the snow and caused great floods. The streams, saturated with 

 ashes, became rivers of mud, and covered the plains with a coating of 

 black. The crater did not become quiet for a year, and then only to 

 break out again in 1864 with increased violence. The dark column 

 of smoke that rose from the crater was visible for miles around, the 

 ash-rain was more formidable than in 1 861, and the detonations were 



