MOUNTAINS OF MEXICO. 



21 



extent, but exceed 6,600 feet in altitude ; even tlie Toluca basin, in the angle 

 formed by the two diverging main ranges, stands at a mean height of 8,500 feet 

 above the sea. Going northwards from Anahuac the continually diverging sierras 

 give more space for elevated plains, and in the northern regions the vast expanses 

 enclosed bj^ the encircling ranges present almost perfectly level surfaces, broken 

 only by low ridges. As they stretch northwards these expanses fall in the direc- 

 tion of the east, and the east sierra itself is much narrower, its mean elevation 

 being 6,500 feet, or about 1,600 feet less than that of the western escarpment. 

 A third range, parallel with, but completely separated from, the two sierras 



Fig. 10. — Relief of Mexico. 

 Scale 1 ; 30,000,000. 



□ 



to 3.300 

 Feet. 



3,300 to 6,600 

 Feet. 



ITeights. 



6,600 to 9,900 

 Feet. 



Depths. 



9,9uO to 16,500 

 Feet. 



16,500 Feet and 

 upwards. 



to 500 

 Fathoms. 



500 to 1.500 

 Fathoms. 



1.500 Fathoms 

 and upwards. 



, 620 Miles. 



enclosing the Mexican tablelands, traverses the Californian peninsula at different 

 elevations and with two interruptions. Isolated eminences, " lost mountains," as 

 they are called, are dotted over the space comprised between the highlands of the 

 American California and the range traversing the peninsula which belongs to 

 Mexico, but which continues the axis of the Sierra Madre. 



The mountains of this peninsula, varying as they do in height and form, must 

 therefore be regarded as forming an orographic system quite distinct from that of 



