precisely the right moment.

The rock left the pouch at astonishing speed, whistling as it traveled
out to sea. Over fifty yards from shore it slapped into the water only a
few feet from a bottle that bobbed there as a target.

Don Scott, nicknamed Scotty, nodded his approval. "Okay, David. Another
hour of practice and you can go hunting Goliath."

Rick grinned. "I'm getting the hang of it," he admitted. "Let's see you
heave another one out there."

The boys had collected a pile of assorted water-polished stones from the
beach near Pirate's Field, and brought them to the front of the big
Brant house facing the Atlantic Ocean.

Scotty selected one of the larger ones, then checked his sling. The
sling was simplicity itself. Two pieces of strong cord were connected to
each side of the pouch, made of heavy canvas about four inches long and
three wide. One string ended in a loop, which Scotty slipped over his
right forefinger. The other string ended in a large knot, which Scotty
held between his forefinger and thumb.

Scotty placed the stone in the pouch and gripped it in his left hand,
holding the stone in place with thumb and forefinger. He took throwing
position, left hand holding the pouch slightly lower than shoulder
height while his right held the strings in the center of his body just
above his belt buckle.

He released the pouch and put his solid weight into the throw.

Rick's lips pursed in a silent whistle. The stone sang shrilly as it
flew up, up, up and far out. Then the trajectory dropped off rapidly and
it fell into the sea.

"Bless Bess!" Rick exclaimed. "Three hundred yards if it was an inch!"

Even Scotty looked a little surprised. "I'm going to quit while I'm
ahead," he announced.

Barbara Brant, a slim, pretty, blond girl a year Rick's junior, hailed
them from the porch, then ran down and joined them. "Hi! What are you
two doing?"

"Scotty just won the rock-throwing championship of the East Coast," Rick
told her.

Barby looked surprised. "He did? I thought you were waiting for Dr.
Gordon?"

"We are, but we decided to try out Scotty's new sling while we were
waiting."

The boys, and in fact the entire scientific staff of Spindrift Island,
had been in a state of excitement for the past few days because of a
telegram received from Dr. John Gordon. Dr. Gordon had been on leave for
some time, working on a special project at a rocket experimental station
in the West. A few days before, Dr. H