114 Part I. Chapter ı. 
mean altitude of from 10,000 to 12,000 feet (3050—3660 m) for two thousand 
miles from Oaxaca far into Arizona. This range has several branches running 
in different directions, the most continuous being the Sierra Madre of the 
Pacific with which runs parallel the Sierra de la Giganta in Lower California 
which has a mean height of about 4000 feet (1220 m). 
Between these two ranges and the central Cordillera to the south is the 
great Mexican tableland, next to those of Tibet and Bolivia, the loftiest 
and most extensive on the globe. From the lacustrine Valley of Mexico, it 
stretches at a nearly uniform elevation of 7500 feet (2300 m) to the Rio Grande 
del Norte. In a total distance of ı225 miles (1971 km), the absolute incline 
is only 3632 feet (1107 m), from 7350 (2240 m) at the capital to 3718 (1133 m) 
at El Paso. With this may be compared the drop of 7350 from the City of 
Mexico to Vera Cruz at sealevel, a distance of about 264 miles (425 km). 
Barrancas, or deep canyons, however, break the uniformity of the tableland. 
The most remarkable of these is the Barranca de Mochititle between Gua- 
dalajara and Tepic and that of Beltran between Guadalajara and Colima. 
The central Cordilleran mountains form cross ridges which culminate in 
Popocatepetl and Ixtaccihuatl. The volcanoes and Orizaba, Jorullo, Colima, 
however, belong to a more recent upheaval, as they are nearly at right angles 
to the main axis of the central plateau. Nearly parallel to these are the 
sierras of Guerrero and those of Oaxaca and Chiapas toward the frontier of 
Guatemala. 
The eastern coast of Mexico, bathed by the Caribbean Sea and the Gulf 
of Mexico is flat, low and sandy except near the mouth of the Tabasco River, 
where at some distance from the coast appear the heights of San Gabriel. 
The coast on the Pacific side, through generally low, is here and there broken 
by spurs extending from the cordilleras to the ocean. Few bays worthy of 
note are found on these coasts, which lack prominent indentations. 
The largest lake in Mexico is Lake Chapala measuring over 80 miles in 
length by 30 in breadth. The Valley of Mexico has seven lakes, one fresh 
and six salt water, the three largest being Chalco, Xochimilco and Texcoco. 
The other lakes worthy of mention are Catemaco in the State of Vera Cruz, 
Cariel and Carpintero in the State of Tamaulipas; Encantado, in Tabasco; 
Bacalor, in Yucatan; Alcuzague, in Colima; Cuitzeo and Patzcuaro, in Michoacan; 
Yuriria, in Guanajuato, and Meztitlan in Hidalgo. Br‘ 
A large number of islands lie off the Mexico coasts. Among the most 
prominent are Carmen, the largest in the Gulf of Mexico; Guadalupe, about 
75 miles (121 km) from the west coast of Lower California, Tres Marias, a = 
group of the same coast; the Revillagigedo group near the Colima coast and 
Alcatraz Island not far from the coast of the State of Michoacan. 
The principal rivers of Mexico are the Rio Grande, 1500 miles (2414 km) 
long forming, from El Paso, Texas to the Sea, the boundary line between 
the United States and Mexico; the Lerma, or Santiago, 5340 miles (869 km) long; 
the Mescala or Balsas, 426 miles (685 km) in length; the Yaqui, 390 miles 
