ON ITS EXTEEIOE. VOLCANOES. 393 



Aguas calientes (21 53' N.), 6262 feet, B. 



Lagos (21 20' N.), 6377 feet, B. 



Villa de Leon (21 07' N.), 6134 feet, B. 



Silao, 5911 feet, B. 



Guanaxuato (21 0' 15" K), 6836 feet, H. 



Salamanca (20 40' N.), 5762 feet, H. 



Celaya (20 38' N.), 6017 feet, H. 



Queretaro (20 36' 39" N.), 6363 feet, H. 



Sa'n Juan del Eio in the State of Queretaro (20 30' K), 



6491 feet, H. 



Tula (19 57' N.}, 6734 feet, H. 

 Pachuca, 8140 feet, H. 

 Moran, near Eeal del Monte, 8511 feet, H. 

 Huehuetoca, at the northern end of the great plain 



of the city of Mexico (19 48' N.), 7533 feet, H. 

 Mexico (19 25' 45" N.), 7469 feet, H. 

 Toluca (19 16' N.), 8824 feet, H. 

 Venta de Chalco, south-eastern end of the plain of 



the city of Mexico (19 16' N.), 7712 feet, H. 

 San Francisco Ocotlan, western end of the great plain 



of Puebla, 7680 feet, H. 

 Cholula, at the foot of the ancient terraced pyramid 



(1 9 02' K), 6906 feet, H. 



La Puebla de los Angeles (19 0' 15"K), 7200 feet, H. 

 The village of Las Vigas marks the eastern end of the 



high plain of Anahuac, 19 37' N. ; the elevation of 



the village is 7814 feet, H. 



Whereas before the commencement of the nineteenth 

 century not a single barometric measurement of altitude 

 had been made in New Spain, it has now become pos- 

 sible to assign, as above, a chain of thirty-two stations 



