264 COSMOS. 



Buenaventura, at a distance equal to that of Berlin from 

 Basle, the Pyrenees from Fontainebleau, or London from 

 Aberdeen. Although, since the commencement of the pre- 

 sent century, the volcanoes of Mexico, New Granada, Quito, 

 Bolivia, and Chili have been visited by some geognosists, the 

 Sangay, which exceeds the Tungurahua in elevation, has un- 

 fortunately remained entirely neglected, in consequence of 

 its solitary position, at a distance from all roads of commu- 

 nication. It was only in December 1849 that an adventurous 

 and highly informed traveller, Sebastian Wisse, after a sojourn 

 of five years on the chain of the Andes, ascended it, and 

 nearly reached the extreme summit of the snow-covered, pre- 

 cipitous cone. He not only made an accurate chronometric 

 determination of the wonderful frequency of the eruptions, 

 but also investigated the nature of the trachyte which, con- 

 fined to such a limited space, breaks through the gneiss. As 

 has already been remarked, 80 267 eruptions were counted in 

 one hour, each lasting on an average 13". 4, and, which is 

 very remarkable, unaccompanied by any concussion percep- 

 tible on the ashy cone. The erupted matter, enveloped in 

 much smoke, sometimes of a gray and sometimes of an 

 orange colour, is principally a mixture of black ashes and 

 rapilli, but it also consists partly of cinders, which rise per- 

 pendiculai'ly, are of a globular form and a diameter of 15 or 

 16 inches. In one of the more violent eruptions, however, 

 Wisse counted only 50 or 60 red hot stones as being simul- 

 taneously thrown out. They usually fall back again into 

 the crater, but sometimes they cover its upper margin, or 

 /isible by their luminosity at a distance, glide down at night, 

 upon a portion of the cone, which, when seen from a great 

 way off, probably gave origin to the erroneous notion of La 

 Condamine, " that there was an effusion of burning sulphur 

 and bitumen." The stones rise singly one after the other, so 

 that some of them are falling down, whilst others have only 

 just left the crater. By an exact determination of time, the 

 visible space of falling (calculated therefore to the margin of 

 the crater) was ascertained to be on the average only 786 

 feet. On Etna, according to the measurements of Sartorius 

 von Waltershausen and the astronomer D. Christian Peters, 

 the ejected stones attain an elevation of as much as 2665 

 60 Cosmos, see page 182. 



