ut, Gaspar says--

"_Hijos mios_; we can't do better than head due westward. That will
bring us out of the _salitral_, somewhere. Luckily there's a sun in the
sky to hold us to a straight course. If we hadn't that for a guide, we
might go zig-zagging all about, and be obliged to spend a night amidst
the saltpetre; perhaps three or four of them. To do so would be to risk
our lives; possibly lose them. The thirst of itself would kill us, for
there's never drinkable water in a _salitral_. However, with the sun
behind our backs, and we'll take care to keep it so, there won't be much
danger of our getting bewildered. We must make haste, though. Once it
mounts above our heads, I defy Old Nick himself to tell east from west.
So let's put on the best speed we can take out of the legs of our
animals."

With this admonition, and a word to his horse, the gaucho goes off at a
gallop; the others starting simultaneously at the same pace, and all
three riding side by side. For on the smooth, open surface of the
_salitral_ there is no need for travelling single file. Over it a
thousand horsemen--or ten thousand for that matter--might march abreast,
with wide spaces between.

Proceeding onward, they leave behind them three distinct traces of a
somewhat rare and original kind--the reverse of what would be made by
travellers passing over ground thinly covered with snow, where the trail
would be darker than the surrounding surface. Theirs, on the contrary,
is lighter coloured--in point of fact, quite white, from the saltpetre
tossed to the top by the hooves of their galloping horses.

The gaucho every now and then casts a glance over his shoulder, to
assure himself of the sun's disc being true behind their backs; and in
this manner they press on, still keeping up the pace at which they had
started.

They have made something more than ten miles from the point where they
entered upon the _salitral_; and Gaspar begins to look inquiringly
ahead, in the hope of sighting a tree, ridge, rock, or other land-mark
to tell where the _travesia_ terminates. His attention thus occupied,
he for awhile forgets what has hitherto been engaging it--the position
of the sun.

And when next he turns to observe the great luminary, it is only to see
that it is no longer there--at least no longer visible. A mass of dark
cloud has drifted across its disc, completely obscuring it. In fact, it
was the sudden darkening of the sky, and, as a conseq