418 Scientific Intelligence. 



are thrown about in the utmost confusion ; while between their intersti- 

 ces the most suffocating vapors arise. 



Lastly, at the foot of the cone are found two more groups of extinct 

 vents. The total number of active vents is about seventy. 



Vapors also find their way through the loose soil, which consists of 

 ashes, sand, and sulphur: their odor was that of burnt sulphur and of 

 rotten eggs ; from which it is to be presumed that they consist of a 

 mixture of the sulphurous and hydrosulphuric acids. The authors next 

 mounted with incredible labor to the summit of the volcano, whose crest 

 is serrated with sharp pyramidal rocks, resembling the teeth of a saw. 

 The inner walls near the top consist of detached blocks and rocks of all 

 sizes; and lower down, of sand and soil with occasional patches of veg- 

 etation. The rocks blackened by time, the profound obscurity, and the 

 vast columns of smoke issuing from an abyss 2460 feet in depth, are 

 described as forming a majestic and terrible scene. 



The authors give the following reasons for believing the eastern cra- 

 ter to be the more ancient. It contains no traces of volcanic fumeroles, 

 and its cone of eruption has entirely disappeared ; its interior walls are 

 but slightly inclined ; and the ridge which separates the two craters, 

 though gently inclined towards the eastern crater, is cut off almost per- 

 pendicularly towards the western. The trachytic rocks of the eastern 

 crater are covered over with sand and pumice, which have evidently 

 been ejected from the western. The eastern crater burst forth near the 

 summit of the ancient Pichincha, and the western on its side. 



The later eruptions of Pichincha have produced nothing but pumice, 

 that being the only rock visible at the surface. Below the Arenal, the 

 sides of the mountain are covered with vegetation, the surface being 

 composed of soil, sand, and pumice, without any debris which can be 

 attributed to recent convulsions. The few masses of rock which pierce 

 the vegetable crust are probably part of the interior stony structure. 

 Yet the eruptions which caused the present craters must have been tre- 

 mendous : solid rock which once formed the summit of Pichincha and 

 the matter thrown from the interior must have reached immense distan- 

 ces, while violent earthquakes must have desolated the neighboring 

 country. Had these been witnessed by man, tradition ought to have 

 preserved the memory of them. But according to the historian of Quito, 

 previous to the eruption of 1539, Pichincha was not known to be vol- 

 canic ; the traditions of the Indians being absolutely silent on the point. 

 The authors think it therefore probable that the eruptions which caused 

 the present craters took place before man inhabited this part of the 

 Cordilleras. The fumeroles of the present cone must also have been 

 obstructed during a great lapse of time ; otherwise the Indians must have 

 noticed great columns of smoke, such as now rise from it. ^he ony 

 known eruptions in 1539, 1577, 1587 and 1660, have all issued from 

 the existing cone ; and to this epoch must be referred the blowing away 

 of the matter which choked the old vent, and the formation of the pre - 

 ent cavities. g , t 



But in spite of history and tradition, it is impossible to believe 

 the vast blocks, more than 12 feet in diameter, which cover part or 

 plain of Ina Quito, distant 3£ leagues, can have been thrown ou 

 the eruption of 1539. There - are no traces of such recent eruptions 



