The pack mules had not yet come up with their driver. The party
foreseeing this, had brought such articles as would be needed for the
night. Taking their blankets and their rifles, together with food and
wood for a fire, they began the slow, and what proved to be painful,
ascent of Sunset Mountain.

A lava field stretched directly in front of them, barring the way. Its
forbidding surface had been riven by the elements until it was a perfect
chaos of black tumult. By the time the Pony Rider Boys had gotten over
this rough stretch, they were ready to sit down and rest. Nance would
not permit them to do so. He said they would have barely time to reach
the crater before dark, as it was, and that they must make the best
speed possible. No one grumbled except Stacy, but it was observed that
he plodded along with the others, a few paces to the rear.

The Professor now and then would point to holes in the lava to show
where explosions had taken place, bulging the lava around the edge and
hurling huge rocks to a considerable distance. As they climbed the
mountain proper they found that Sunset, too, had engaged in some gunnery
in those far-away ages, as was shown by many lava bombs lying about
the base.

The route up the mountain side was over a cider-buried lava flow, the
fine cinders under foot soon making progress almost a torture. Tad was
the first to stand on his head as his feet went out from under him.
Stacy, in a fit of uproarious laughter, did the next stunt, that of
literally standing on his right ear. Chunky tried to shout and got
his mouth full of cinders.