308 Notice of Active and Extinct Volcanos. 



Presentation. Near this habitation there is a brook which dis- 

 engages sulphuretted hydrogen. It is more than twenty-three 

 feet in breadth, and is the most abundant hydro-sulphureous wa- 

 ter which I have ever seen.* 



" The five active volcanos just noticed appear to be connected 

 by a chain of intermediate cones running in a parallel direction, 

 and exhibiting evident indications of a similar origin." 



" Thus Orizaba is connected with Popocatepelt, by the 

 Coffre de Perote, and with Jorullo, by the extinct volcano of 

 Mexico, otherwise called Iztaccihualt ;" the substance of 

 which they are composed is trachyte through which the vol- 

 canic vents act. 



In Guatimala and Nicaragua between Mexico and the 

 isthmus of Darien, between 10° and 15° of north latitude, 

 twenty-one active volcanos are enumerated ; the direction of 

 the chain is parallel with that of the Cordilleras. 



South of the isthmus there are three volcanos in Pasto, 

 three in Popayan, and five in Quito. 



"The connexion of that near the town of Pasto with those of 

 the province of Quito, was shewn in a striking manner in 1797. 

 A thick column of smoke had proceeded ever since the month 

 of November, 1796, from the volcano of Pasto ; but to the 

 great surprise of the inhabitants of the city of that name, the 

 smoke suddenly disappeared on the 4th of February, 1797- This 

 was precisely the moment, at which, sixty-five leagues farther 

 south, the city of Riobamba, near Tunguragua, was destroyed 

 by a tremendous earthquake. 



" Between Quito and Chili only one volcano is known to occur, 

 and this is situated in Peru." 



" Nevertheless the frequent occurrence of earthquakes in the 

 intermediate country renders it probable, that no natural separa- 

 tion exists between the two provinces, but that the same opera- 

 tions are in fact proceeding throughout the whole intermediate 

 tract. 



" It appears probable, says Humboldt, that the higher part of 

 the kingdom of Quito, and the neighboring Cordilleras, far from 



* Mr. Poulett Scrope has given a different theory as to the formation of the 

 volcanic mountain and hornitos of Jorullo, for which see his Considerations on 

 volcanos or the abstract of it, in our last No. 



