or log?"

It was almost too dark to see, but I leaned over the rail and swept
the water with my hand.

Instantly something smooth glided under it, like the back of a great
fish, and I jerked my hand back to the tiller. At the same moment the
whole surface of the water seemed to begin to purr, with a sound like
the breaking of froth in a champagne-glass.

"What's the matter with you?" asked Halyard, sharply.

"A fish came up under my hand," I said; "a porpoise or something--"

With a low cry, the pretty nurse clasped my arm in both her hands.

"Listen!" she whispered. "It's purring around the boat."

"What the devil's purring?" shouted Halyard. "I won't have anything
purring around me!"

At that moment, to my amazement, I saw that the boat had stopped
entirely, although the sail was full and the small pennant fluttered
from the mast-head. Something, too, was tugging at the rudder,
twisting and jerking it until the tiller strained and creaked in my
hand. All at once it snapped; the tiller swung useless and the boat
whirled around, heeling in the stiffening wind, and drove shoreward.

It was then that I, ducking to escape the boom, caught a glimpse of
something ahead--something that a sudden wave seemed to toss on deck