three paces from it, and without my horse's foot having touched it. Its
long roots stretch out horizontally in the ground, and the approaching
tread of a horse or man is communicated through them to the plant, and
produces this singular phenomenon. When the danger is gone by, and the
earth ceases to vibrate, the mimosa may be seen to raise its head again,
but quivering and trembling, as though not yet fully recovered from its
fears.

I had ridden on for three or four hours, following the track I had so
fortunately discovered, when I came upon the trace of a second horseman,
who appeared to have here joined the first traveller. It ran in a parallel
direction to the one I was following. Had it been possible to increase my
joy, this discovery would have done so. I could now entertain no doubt
that I had hit upon the way out of this terrible prairie. It struck me as
being rather singular that two travellers should have met in this immense
plain, which so few persons traversed; but that they had done so was
certain, for there was the track of the two horses as plain as possible.
The trail was fresh, too, and it was evidently not long since the horsemen
had passed. It might still be possible to overtake them, and in this hope
I rode on faster than ever, as fast, at least, as my mustang could carry
me through the thick grass and flowers, which in many places were four or
five feet high.

During the next three hours I passed over some ten or twelve miles of
ground, but although the trail still lay plainly and broadly marked before
me, I say nothing of those who had left it. Still I persevered. I must
overtake them sooner or later, provided I did not lose the track; and that
I was most careful not to do, keeping my eyes fixed upon the ground as I
rode along, and never deviating from the line which the travellers had
followed.