inta closed to within twenty yards, an easy bowshot. Rick mentally
timed the rise and fall of the craft on the swell. Then, as it broached
slightly, he had a clear shot at the helmsman. Kneeling, he drew swiftly
and loosed. The shaft caught the Moro in the hollow of the shoulder and
pinned him back against the stern transom.

Rick reached for another arrow in the smooth rhythm Shannon had taught
him, but the rhythm was abruptly shattered by a sudden blast almost in
his ear! He whirled swiftly to meet the new threat, just in time to see
Zircon open the breech of the saluting cannon and extract a smoking
shell.

For an instant Rick wondered if the scientist had taken leave of his
senses. He saw Zircon ram home a blank cartridge and close the breech.

Then, suddenly, the action made sense to Rick. For Zircon upended the
cannon muzzle and poured in a box of tacks!

The scientist depressed the muzzle, sighted calmly, and pulled the
lanyard. A swath of tacks spewed into the bow of the nearest vinta
bringing a chorus of pirate yells. The craft swerved away.

Shouting with delight at the scientist's ingenuity, Rick jumped to
Zircon's side. Working together, they fired box after box of tacks, and
saw the vintas slowly clear the way.

The Moros could face cold steel or hot lead without a qualm, but the
fierce, stinging tacks were too much, and too unexpected. They failed to
press the attack at the crucial moment and the _Swift Arrow_ slipped
through the line.

As Zircon had predicted, one engine gave them enough speed to get clear,
once the Moros had lost the advantage of a favorable wind. Scotty fired
a few more shots at the vintas within range, then dropped to the deck.
The fight was over.

The four gathered in the pilothouse and the three boys stared at Zircon
with mixed admiration and amusement.

"It's nothing," the big physicist said modestly. "You see, in my
lifetime I have been an avid reader. At one time, while at the
university, I read of some round-the-world traveler using tacks in a
signal gun. So I disclaim originality."

"My 'Worrold Alm-in-ack' not saying about this," Chahda said, grinning.
"Is pretty lucky you have good memory for other books, Professor!"

Rick looked back at the vintas, rapidly falling astern. The pirates were
well beyond gunshot now. "Victory at Sea," he proclaimed. "Thanks to the
professor's college education!"

CHAPTER XI

The Dancing Pirates

The _Swift Arrow_ rode at