him, and in a low whisper Carnes reported his
discovery. The doctor went back with him and together they renewed the
search. The slope of the hill was almost sheer and Carnes looked
dubiously over the edge.

"I wish we had brought the parachutes," he whispered to the doctor.
"We could have taken the ropes off them and you could have lowered me
over the edge."

Dr. Bird chuckled softly and tugged at his middle. Carnes watched him
with astonishment in the dim light, but he understood when Dr. Bird
thrust the end of a strong but light silk cord into his hands. He
looped it under his arms and the doctor with whispered instructions,
lowered him over the cliff. The doctor lowered him for a few feet and
then stopped in response to a jerk on the free end. A moment later
Carnes signaled to be drawn up and soon stood beside the doctor.

"That's the place all right," he whispered. "The whole cliff is
covered with creepers and there is a tree growing right close to it.
If we can anchor the cord here, I think that we can slide down to a
safe hold on the tree."

A tree stood near and the silk cord was soon fastened. Carnes
disappeared over the cliff and in a few moments Dr. Bird slid down the
cord to join him. He found the detective seated in the crotch of a
tree only a few feet from the face of the cliff. From the cliff came a
pronounced murmur of voices. Dr. Bird drew in his breath in excitement
and moved forward along the branch. He touched the stone and after a
moment of searching he cautiously raised one corner of a painted
canvas flap and peered into the cliff. He watched for a few seconds
and then slid back and silently pulled Carnes toward him.

* * * * *

Together the two men made their way toward the cliff and Dr. Bird
raised the corner of the flap and they peered into the hill. Before
them was a cave fitted up as a cross between a laboratory and a
hospital. Almost directly opposite them and at the left of a door in
the farther wall was a ray machine of some sort. It was a puzzle to
Carnes, and even Dr. Bird, although he could grasp the principle at a
glance, was at a loss to divine its use. From a set of coils attached
to a generator was connected a tube of the Crookes tube type with the
rays from it gathered and thrown by a parabolic reflector onto the
space where a man's head would rest when he was seated in a white
metal chair with rubber insulated feet, which stood beneath it. An