reeze--he walked to and fro in double quick
time. The only moments when he remained motionless were at those
intervals when it was necessary for him to pause and call out the usual
phrase: "_Alerta, centinela_!"

"I am sorry for the poor devil!" said Costal, "we must send him to keep
guard in the next world."

The wall behind which they had halted, although tumbled down and in
ruins, still rose sufficiently high to screen the party from the eyes of
the sentinel. Moreover, between the latter and the ruin, the ground was
thickly studded with aloe plants and bushes of wild wormwood.

"Let us first get rid of the sentry," said Costal; "that accomplished,
scatter yourselves among the bushes, and leave the rest to me."

On giving this counsel, the Zapoteque borrowed a sling from one of the
Indians, in which he placed a stone carefully chosen. Then ordering two
others to make ready their bows, he continued, addressing himself to Don
Cornelio--

"You, Senor Captain, can give the signal. Take two stones--strike them
together so that the fellow may hear you--strike them twice. And you,"
continued he, turning to the bowmen, "on hearing the second stroke, take
good aim, and let fly your arrows."

Costal stood holding the sling in readiness. It was one of those rare
occasions when the bow and the sling serve better than any kind of
firearm.

Lantejas brought the two stones into collision with a loud crack.

The sentry heard the concussion, suddenly halted in his steps, brought
his piece to the "ready," and stood listening.

The Captain gave the second signal. The stone and arrows hissed
simultaneously through the air; and, struck by all three, the soldier
fell dead without even uttering a cry.

"Go! scatter yourselves among the bushes," cried Costal, hurriedly; "the
rest I can manage better without you."

Don Cornelio and the Indians, in obedience to Costal's injunction,
glided from behind the wall, and crept forward among the aloes.

As they were advancing, directly in front of them, there arose the cry,
"_Alerta, centinela_!" It came from the place where the sentry had just
fallen; and Don Cornelio, on looking in that direction, perceived, to
his horror and surprise, that the man was once more upon his feet, and
walking his rounds as if nothing had happened!

Lantejas turned to demand an explanation from Costal, but the latter was
nowhere to be seen. The Captain then faced towards the other Indians;
but th