ON ITS EXTERIOR. VOLCANOES. 269 



pieces of granite which, in a district otherwise entirely 

 devoid of granite for a great distance, I found imbedded 

 in the lava which had poured forth from the principal 

 volcano of Jorullo. 



The following table contains the latitudes and alti- 

 tudes of the series of Mexican volcanoes which have been 

 elevated over a fissure running from sea to sea and 

 crossing the fissure of elevation of the great mountain- 

 chain. 



Series from E. to \V. Geogr. Latitude, 



Volcano of Orizaba ... 19 2' 17" 17,879 feet. 



Nevado Iztaccihuatl . . . 19 10 3 15,705 



Volcano Popocatepetl . . 18 59 47 17,726 



Volcano of Toluca . . . 19 11 33 15,168 



Volcano of Jorullo ... 19 9 4,265 



Volcano of Colima ... 19 20 13,003 



The westward prolongation of this parallel of volcanic 

 activity in the tropical zone in Mexico conducts, at a 

 distance of 440 miles from the coast, to a group of 

 islands in the Pacific called Eevillagigedo, in the vicinity 

 of which Collnet has seen pumice floating, and perhaps, 

 yet farther, to the great volcano of Mouna Eoa (19 28' 

 lat.) 3360 miles distant, without the upheaval of any 

 intervening islands. 



The linear group of Quito and New Granada com- 

 prises a volcanic zone which extends from 2 S. to 

 nearly 5 N. latitude. The extremities of the area, in 

 which the reaction of the earth's interior against the 

 surface now manifests itself, are the uninterruptedly 

 active volcano Sangay, and the Paramo and Volcan de 



