r;
and once at an earlier period of his life on an expedition of less
pleasant remembrance, when, as a captive himself, he was carried up the
Pilcomayo by a party of Guaycuru Indians, from whom he was fortunate in
making escape.

His knowledge of the cave's locality, however, was not obtained during
his former and forced visit to the district they are now traversing; but
in that made along with the hunter-naturalist; who, partly out of
curiosity, but more for geological investigation, had entered and
explored it.

"It's by the bank of a little _arroyo_ that runs into the Pilcomayo,
some three or four miles above the big river. And, as I take it, not
much further from where we are now. But we must make a cross-cut to
reach it in the quickest time."

This Gaspar says as they part from the barometer-tree. Following out
his intention he heads his horse towards the open plain, and forsakes
the Indian trail, the others following his lead.

They now go in full gallop, fast as their horses can carry them; for
they have no longer any doubts about the coming on of a _tormenta_. The
forecast given them by the flowers of the _uinay_ is gradually being
made good by what they see--a dun yellowish cloud rising against the
horizon ahead. The gaucho well understands the sign, soon as he sees
this recognising it as the dreaded dust-storm.

It approaches them just as it had done the Indians. First the
atmosphere becoming close and hot as the interior of an oven; then
suddenly changing to cold, with gusts of wind, and the sky darkening as
though the sun were eclipsed.

But, unlike the others, they are not exposed to the full fury of the
blast; neither are they in danger of being blinded by the sulphureous
dust, nor pelted with sticks and stones. Before the storm has thus
developed itself they reach the crest of the cliff overhanging the
_arroyo_; and urging their horses down a sloping path remembered by
Gaspar, they get upon the edge of the stream itself. Then, turning up
it, and pressing on for another hundred yards, they arrive at the
cavern's mouth, just as the first puff of the chilly wind sweeps down
the deep rut-like valley through which the _arroyo_ runs.

"In time!" exclaims the gaucho. "Thanks to the Virgin, we're in time!
with not a second to spare," he adds, dismounting, and leading his horse
into the arching entrance, the others doing the same.

Once inside, however, they do not give way to inaction; for Gasp