about on the slippery ice tried to ascertain its thickness and how far
under water it extended. The boys soon tired of sitting idle in the
boat and, as they had been forbidden to land on the treacherous ice of
the reef, cast about for something to do. The professor soon provided
a digression.

"Look there," he suddenly shouted, pointing at a black triangular
shaped object that was moving about on the green water a short
distance from the boat.

"What can it be?" wondered Billy.

"Some sort of rare fish, I don't doubt," rejoined the professor.
"Let's row out and see."

The boys, nothing loath, shoved off, and as Ben and the crew of the
boat were far too busy sounding and poking about on the reef to notice
them, they rowed off unobserved.

The triangular object proved elusive, and after rowing some time, the
boys found they had come quite a distance from the ship without
getting much nearer to it. Suddenly a great, shining black back curved
itself out of the water and the boys saw that the sharp triangular
thing was an immense dorsal fin attached to the back of a species of
whale they had not so far seen, although they had sighted many
varieties since entering the Antarctic regions.

"Let's give it a shot," cried Billy, and before any one could stop
him, the young reporter fired at the creature.