346 PLATFORMS OF THE ANDES. 
an immense table-land, having an elevation which 
varies from 6562 to $202 feet above the level of 
the sea. | 
The chain of mountains which forms this vast plain 
is continuous with the Andes of South America. In 
the southern hemisphere the cordillera is every where 
broken up by fissures or valleys of small breadth ; 
but in Mexico it is the ridge itself that constitutes the 
platform. In Peru the most elevated summits form 
the crest of the Andes, while in the other the pro- 
minences are irregularly scattered over the plain, 
and have no relation of parallelism to the direction 
of the cordillera. In Peru and New Grenada there 
are transverse valleys, having sometimes 4590 feet 
of perpendicular depth, which entirely prevent the 
use of carriages; while in New Spain vehicles are 
used along an extent of more than 1726 miles. The 
general height of the table-land of Mexico is equal 
to that of Mount Cenis, St Gothard, or the Great St 
Bernard of the Swiss Alps; and to determine this 
circumstance Humboldt executed five laborious ba- 
rometrical surveys, which enabled him to construct 
a series of vertical sections of the country. : 
In South America the cordillera of the Andes pre- 
sents plains completely level at immense altitudes, 
such as that on which the city of Santa Fe de Bo- 
gota stands, that of Caxamarca in Peru, and those 
of Antisana, which exceed in height the summit of 
the Peak of Teneriffe. But all these levels are of 
small extent, and being separated by deep valleys 
are of difficult access. In Mexico, on the other 
hand, vast tracts of champaign country are so 
approximated to each other as to form but a single 
plain occupying the elongated ridge of the cordil- 
