VIENTE DE ZONDA.
In a preceding chapter I made reference to the _viente de zonda_,
or zonda wind; and as the history of it is imperfectly known in the
northern continent, I will here speak of it to some extent.
The _viente de zonda_ may be called a local wind, as it blows only in
the vicinity of the province of San Juan, the town where the following
observations were made.
San Juan, the capital of the province, lies at the eastern base of
the Andes, three or four leagues distant from the outer sierra, south
latitude 31° 4′ (Molina), longitude 68° 57′ west (Arrowsmith). Behind
the first range in a valley are four or five farms, which constitute
the hamlet of Zonda, from which the wind is named. It blows at all
seasons, though during July and August (midwinter) it is most frequent.
This wind is hot and parching to the skin, and brings with it clouds of
dust and fine sand.
All persons leave their work, and seek refuge in their houses, while
frequently the huts of the gauchos are blown down by the force of
the wind. Most persons are troubled with severe headaches. Those who
have been suffering from diseases of the heart find their complaints
greatly aggravated, and frequently there are cases of sudden death.
Three or four years since, five persons fell dead during the _zondas_
in the month of August. The wind lasts sometimes two or three hours;
at other times, forty-eight hours, though this long duration is rare.
While the _zondas_ is at its height, a few puffs of cold air from the
south announce a change, and immediately the weather-cock veers from
east and west to north and south, and a cold wind, equally as strong as
the hot _zonda_, then prevails from the south. All nature is refreshed
by the change, and men resume their abandoned labors.
In searching through the works of the very few authors who have
visited the interior of the Argentine states (all but one or two of
whom were Europeans), I find that only one mentions the existence of
this phenomenon; and he did not, probably, visit the town where my
observations were made, which locality is considered by the natives as
the northern limit of the _zondas_.
John Miers, the author of an interesting work on the Provinces of La
Plata and Chili, remained a short time in Mendoza. He states that this
southern locality is annoyed by winds that blow during the summer
months from the valley of Zonda, and notes the fact that two dark
clouds came from the north-west, and hovered over the town during the
greater part of the night, and in the morning everything that had been
exposed to the air was covered with fine sand, which was of a light
gray color, and slightly magnetic. It was Miers’s opinion that “a
_souffrière_, or active volcano,” existed to the northward of San Juan,
from which the hurricanes and showers of sand originated. Had Mr.
Miers visited San Juan, his view of the position of the volcano would,
undoubtedly, have been changed; for though the _zondas_ reach Mendoza
to the south, the direction of the wind when it strikes that place
differs from the line it follows when it rushes with violence upon the
northern town. At San Juan it comes due west from the Andes. Hence the
starting-point of the _zonda_ cannot be to the north of the town, as
Miers conjectured. According to the account of the natives, the _zonda_
of San Juan does not cover a broader space than ten or fifteen miles
after it leaves the sierra of Zonda.
Taking this into consideration, in connection with Miers’s statement
that the Mendoza _zonda_ comes from the north-west, differing, as it
will be seen, four points from the northern town, we may infer that the
Mendoza and San Juan _zondas_ do not blow at the same time. If this is
true, it is an interesting fact, showing that this peculiar wind does
not always follow the same track.
Miers further states that these are summer winds in Mendoza. From
personal observation, and by reliable accounts of educated San
Juaninos, I found that they were more particularly the winter winds;
at least they are more frequent during that season. Invalids suffering
from pneumonical diseases and complaints affecting the heart and liver,
anticipate the month of August (midwinter) with consternation, and
their anxiety is not quieted until they have passed through the dreaded
ordeal.
While passing the winter in San Juan, I noted the courses of upwards
of twenty _zondas_. Some were of short duration; others lasted eighteen
or twenty hours.
During the latter part of August, as I was standing upon the saline
desert, a few miles east of San Juan, my attention was attracted by a
cloud of dust that appeared to roll through the air as it approached
me. I started for a shelter, and had hardly reached it when the _zonda_
swept past, filling the air with fine yellow sand. The temperature of
the previously sultry atmosphere suddenly rose many degrees, and the
occupants of the neighboring huts were affected with severe headaches.
I noted, with a compass, the course of the wind, which was west. All
night and through the following day and night, the wind continued
blowing with undiminished force. Each hour the vane beside the hut
was consulted, and the same course as at first was always observed.
A few hours before the wind ceased the sand showers were exhausted.
The greatest heat was during the first few hours; and this is always
the case if the _zonda_ commences during the day. After continuing
for thirty-six hours the change came. It was instantaneous. The hot
wind seemed cut off at right angles by a cold wind from the south. The
change could not have occupied more than forty seconds. The south wind
lasted twenty hours, and was as violent as the hot _zonda_. In speaking
of the Mendoza _zondas_, Miers does not mention the succession of the
south wind. It is easy to comprehend that, after so large an area has
become filled with heated air, the effect will be felt in the cooler
regions of the south, and a strong current from that direction will
rush in to restore the atmospheric equilibrium. Hence the cause of the
south wind succeeding the _zonda_.
Miers believed that the origin of the _zondas_ was volcanic, and a
corroboration of his views is found in the work of Sir Woodbine Parish,
in which he states that the volcano Penguenes, which is situated about
one hundred miles south-west from Mendoza, and reaches an altitude of
nearly fifteen thousand feet above the level of the sea, emits clouds
of ashes and pumice-dust. This dust is carried by the winds as far as
Mendoza, but these clouds do not strike the town with the force of
the San Juan _zonda_. The pumice-dust is _borne_ along by variable
winds. From this fact we may infer that the fine sand of the _zondas_
comes from a similar source. The most important question is, _Where
originates the hot and parching wind that always accompanies, and is
peculiar to, the zondas?_ The old guides, who are familiar with the
valleys of the Andes, informed me that these winds blow from off the
main snow-clad ridge of that great chain of mountains, and expressed
their surprise at the fact “that from a cold region comes a burning
wind.”
Strong and steady winds generally follow a direct line. This fact
is characteristic of the _zondas_. If Miers’s conjecture be true
regarding the origin of these winds, the position of the volcano, or
_souffrière_, might be found by observing the following suggestion,
bearing in mind that the Mendoza wind comes from the _north-west_, and
the San Juan _zonda_ from the _west_. That point where two lines--one
running west from the northern town, the other _north-west_ from the
southern town--will intersect, is the starting-point of the sand
clouds, if not of the accompanying hot wind.
Looking upon the map of South America, we find in the Cordillera of
the Andes, between the latitudes of San Juan and Mendoza, four peaks
marked as doubtful volcanoes: Limari, directly west of San Juan;
Chuapu, thirty miles farther south; and near the half-way point of the
two towns, Ligua. To the north of west of Mendoza stands prominent the
lofty Aconcagua, that has been estimated by two English captains to
have an elevation of twenty-three thousand nine hundred feet. The point
of intersection of the west and north-west _zonda_ lines is in the
vicinity of Limari and Chuapu, and, if not either of these, the _zonda_
volcano is a near neighbor to them.