gives his
horse a dig in the ribs, with spur rowels of six inches diameter, and
starts off at a swinging pace, the others after.

And now side by side go all three, splashing and spattering through the
mortar-like mud, which, flung up in flakes by their horses' hoofs, is
scattered afar in every direction.

Half an hour of quick cantering brings them back upon the Pilcomayo's
bank; not where they had parted from it, but higher up, near the mouth
of the _arroyo_. For Gaspar did not deem it necessary to return to that
prophetic tree, whose forecast has proved so unfailing. To have gone
back thither would have been a roundabout of several miles, since they
had made a cross-cut to reach the cavern; and as on the way they had
seen nothing of the Indian trail, it must needs have continued up the
river.

But now, having reached this, they cannot tell; for here, as on all the
plain over which they have passed, is spread the same coating of
half-dried dirt, fast becoming drier and firmer as the ascending
tropical sun, with strengthened intensity, pours his hot beams upon it.
It has smothered up the Indian's trail as completely as it snow several
inches deep lay upon it. No track there, no sign to show, that either
horses or men ever passed up the Pilcomayo's bank.

"_Caspita_!" exclaims the gaucho, in spiteful tone. "It is as I
anticipated; blind as an old mule with a _tapojo_ over its eyes. May
the fiends take that _tormenta_!"

CHAPTER THIRTY TWO.

STOPPED BY A "RIACHO."

For a time the trackers remain at halt, but without forsaking their
saddles, pondering upon what course they should pursue, or rather, what
direction they ought to take.

Only a short while are they undecided. It seems good as certain that
the Indians have kept to the river, for some distance further on, at all
events. Therefore, it will be time enough to enter upon a more
prolonged deliberation, when they come to a point where this certainty
ceases. Thus reflecting, they start off afresh, with their horses'
heads as before.

Going at good speed as ever, in a few minutes they arrive at the
confluence of the _arroyo_ with the greater river; the former here
running between banks less "bluffy" than above, where it passes the
cavern. Still they are of sufficient elevation to make a sharp descent
towards the channel of the stream, and a corresponding ascent on its
opposite side. But instead of an impediment, the trackers find this an
adva