eat of the Equator is offset by the coolness of the
rarefied air of high elevations above sea-level. This structure is the
dominant note of the scheme of Nature in Mexico--as it is in Peru and
other similar countries--and the anthropo-geographical conditions are
correspondingly marked. The region first passed is known as the _tierra
caliente_, or hot lands. Its climatic limit extends up the slopes of
the Sierras to an elevation of some 3,000 feet or more, embracing the
lowlands, hot and humid generally, of the whole of the Gulf coast and
of the peninsula of Yucatan, all of which regions are subject to true
tropical conditions--the dense forests, the great profusion of animal
life, the wonderful abundance and colour of Nature, and in places the
swamps and their accompanying malarias, shunned by the traveller. But
yellow fever and malaria are much less dreaded now than heretofore. In
the city of Vera Cruz and in Tampico the new era of sanitation, brought
about by British and American example and seconded by the Mexican
authorities, has almost banished these natural scourges.

Rising from the _tierra caliente_, the road enters upon the more
temperate zone, the _tierra templada_, extending upwards towards the
Great Plateau. The limit of this climatic zone is at the elevation of
6,000 feet above sea-level, and here are evergreen oaks, pine, and the
extraordinary forms of the organ cactus, as well as orchids. It is,
indeed, a transition zone from the hot to the cold climates, and the
zone embraces the greater part of the area of Mexico. Rising rapidly
thence up to and over the escarpments of the Sierra Madre and the high
plains, we shall enter upon the _tierra fria_ or cold lands, ranging
from 6,000 feet to 8,000 feet above sea level. Above this rise the high
summits of the Mexican Cordilleras, with their culminating peaks, some
few of which penetrate the atmosphere above the limit of perpetual
snow. Thus, three diverse climatic zones are encountered in Mexico,
which, ever since the advent of the Spaniards, have been designated as
the _tierra fria_, _tierra templada_, and _tierra caliente_
respectively. These conditions, as will be seen later, are also
encountered upon the Pacific slope.

We now ascend the steep upper zone of the Sierra Madre, and cross it,
descending thence to the Great Plateau or _mesa central_, the
dominating topographical feature of the country. Here lies the real
Mexico of history, and here is the main