?"

"Sulphur, I guess, and gases from the volcano. The wind blew 'em over
this way. They're not dangerous, as long as there is no carbonic acid
gas given off, and I don't smell any of that, yet. Say, Ned, it's
erupting all right, isn't it?"

"I should say so!" cried his chum.

"Put us a little to one side, Mr. Damon," called Tom to his friend, who
was in the pilot house. "I can't get good pictures through so much
smoke. It's clearer off to the left."

"Bless my bath robe!" cried the odd man. "You're as cool about it, Tom,
as though you were just in an ordinary race, at an aeroplane meet."

"And why shouldn't I be?" asked our hero with a laugh, as he stopped
the mechanism of the camera until he should have a clearer view of the
volcano. "There's not much danger up here, but I want to get some views
from the level, later, and then--"

"You don't get me down there!" interrupted Mr. Nestor, with a grim
laugh.

They were now hovering over the volcano, but high enough up so that
none of the great stones that were being thrown out could reach them.
The column of black smoke, amid which could be seen the gleams of the
molten fires in the crater, rolled toward them, and the smell of
sulphur became stronger.

But when, in accordance with Tom's suggestion, the airship had been
sent over to one side, they were clear of the vapor and the noxious
gas. Then, too, a better view could be had of the volcano below them.

"Hold her down!" cried Tom, as he got in a good position, and the
propellers were slowed down so that they just overcame the influence of
a slight wind. Thus the Flyer hovered in the air, while below her the
volcano belched forth red-hot rocks, some of them immense in size, and
quantities of hot ashes and cinders. Tom had the camera going again
now, and there was every prospect of getting a startling and wonderful,
as well as rare series of moving pictures.

"Wow! That was a big one!" cried Ned, as an unusually large mass of
rocks was thrown out, and the column of fire and smoke ascended nearly
to the hovering craft. A moment later came an explosion, louder than
any that had preceded. "We'd better be going up; hadn't we Tom?" his
chum asked.

"A little, yes, but not too far. I want to get as many near views as I
can."

"Bless my overshoes!" gasped Mr. Damon, as he heard Tom say that. Then
he sent some of the vapor from the generating machine into the gas bag,
and the Flyer arose slightly.

Ned looked i