t you here," declared Dad. "You'll
go along with us."

Before starting on the final thousand feet of the descent the trappings
were removed from the horses, after which the animals were staked down
so that they might not in a moment of forgetfulness fall over the wall
and be dashed to pieces on the rocks below.

Dad got out his climbing ropes, the boys watching the preparations with
keen interest.

"Are you going down, Professor?" asked Tad smilingly.

"Certainly I am going down. I for one have no intention of remaining
to watch the stock," with a grim glance in Chunky's direction. Chunky
saw fit to ignore the fling at him. He was gazing off across the chasm
at the Temple of Isis, which at that moment absorbed his full attention.

"Now I guess we are ready," announced the guide finally. "I will go
first. In places it will be necessary to cling to the rope. Don't
let go. Then, in case you stumble, you won't get the nasty fall that
you otherwise would be likely to get."

Away up, just below the Indian Garden, they picked up the slender trail
that led on down to the roaring river. They had never had quite such a
climb, either up or down.

Every time they looked down they saw a possible fall upon rough,
blade-like granite edges.

"We'd be sausage meat if we landed on those," declared Chunky.

"You are likely to go through the machine if you don't pay closer
attention to your business," answered Dad.

Carefully, cautiously, laboriously they lowered themselves one by one
over the steep and slippery rocks, down, down for hundreds of feet until
they stood on the ragged edge of nowhere, a direct drop of several
hundred feet more before them.

The guide knew a trail further on, so they crept along the smooth wall
of the Canyon with scarcely room to plant their feet. A misstep meant
death.

"Three hundred feet and we shall be there," came the encouraging voice
of the guide. "Half an hour more."

"I could make it half a minute if I wanted to," said Stacy. "But I
don't want to. I feel it my duty to stay and look after my friends."

"Yes, your friends need you," answered Ned sarcastically. "If they
hadn't I never should have pulled you out of the hole in the crater."

"I was just wondering how Chunky could resist the temptation of
falling in here. He'll never have a better opportunity for making a
clean job of said Walter.

"He has explained why," replied Tad. "We need him. Of course we do.
We ne