26 



MEXICO, CENTRAL AMERICA, WEST INDIES. 



eruptive rocks, between whose foldings are enclosed lacustrine basins wbicb are 

 still flooded, and in which quaternary alluvia have been deposited. 



San Andres or Tajimaroa, a group of volcanoes lying east of Morelia, still 

 presents on one of its summits a funnel filled with boiling water, and emitting 

 copious sulphurous vapours. These vapours change to sulphates the argillaceous 



Fio-. 11. — JORULLO, ACCOEDING TO HuMBOLDT. 

 Scale 1 : 180,000. 



Section. 



Plan. 



3 Miles. 



clays of the surrounding district, and thus are periodically undermined the huts of 

 the workmen occupied in collecting the mud richly charged with sulphur. 



The Cerro de las Humaredas, another trachytic cone, owes its name to its 

 abundant f umaroles. Near it springs a geyser from the very summit of a siliceous 

 cone gradually deposited by the jets of boiling water. One of the craters, over 

 13,200 feet high, takes the name of Chillador, or " Whistler," from the hissing 

 sound of the vapours escaping from its mouth. In 1872 a series of violent earth- 

 quakes was followed by the appearance of a new Chillador by the side of the other. 



