me places are
traversed by deep _barrancas_, or gullies, worn down perpendicularly
through the soil; and woebetide the unlucky horseman who may be
journeying along the bottom of one of these when the wave of water
comes down from some sudden cloud-burst in the mountains, which happens
not infrequently. Incautious Indians and _peones_, also, who have taken
up their lodging in some cave or dug-out of the banks of the torrential
rivers of the plateau, or who have laid drunk upon the sun-baked
river-bed, are often surprised by the waters, and their bodies are
recovered miles away, stranded upon some sand-bar. This serves as
giving an idea of the sudden and rapid flow of water from the mountains
under the torrential rains; and a good example of a river subject to
such a regimen is that of the Nazas. I have crossed the dry bed of this
river at Torreon on various occasions on horseback, but on the return
journey an hour afterwards the horse was swimming, or, when the current
was too fierce, it was necessary to make a long detour to the bridge,
for the torrent was raging 300 feet wide from bank to bank.

The average rainfall varies greatly for different parts of the country.
For example, in the City of Mexico a year's mean fall may be 25 inches,
whilst in Monterrey, some 500 miles to the north, it would reach 130
inches. In the dry season, however, no rain falls in any of the three
zones of hot, temperate, or cold lands. Snowfall is very rare as far
south as the City of Mexico, but is not unknown. In the cities of the
great plateau, to the north, it is almost equally rare, occurring
perhaps once or twice in a lifetime. When such does take place it
affords an unwonted spectacle for the _peones_, and causes them to wrap
themselves in their _serapes_ and muffle up their mouths as if they
were in the polar regions, rather than experiencing a momentary fall of
temperature! A scene of this nature occurred during my stay in Lerdo,
one of the towns of this region, and is well depicted in the
accompanying view. The low rainfall of the extreme north of Mexico, of
two to three inches, on the border of Arizona, and the excessive fall,
reaching 156 inches, on the Isthmus of Tehuantepec, with the high rate
for Monterrey and the moderate fall for the capital, show how
remarkable are the hygrometric conditions due to topography. The
maximum rainfall is only exceeded in very few regions of the globe.

[Illustration: A RARE OCCURRENCE: SNOWFALL