the trip through the air, and had many thrills fighting the savage
Eskimos. Finally, they succeeded in passing over the exact spot of the
North Pole during a violent snowstorm.

Not satisfied with their experiences after conquering the North, the
adventurers set out for the Antarctic regions in a submarine boat. This
trip, even more remarkable than the first, took them to many strange
places in the South Atlantic. They were trapped for a time in the
Sargasso Sea, and they walked on the ocean floor in new diving suits,
one of the professor's marvelous inventions.

It was on the voyage to the south that, coming to the surface one day,
the adventurers saw a strange island in the Atlantic Ocean, far from
the coast of South America. On it was a great whirlpool, into which the
_Porpoise_, their submarine boat, was nearly drawn by the powerful
suction.

The chasm might lead to the center of the earth, it was suggested, and,
after thinking the matter over, on their return from the Antarctic,
Professor Henderson decided to build a craft in which they might solve
the mystery.

The details of the voyage they took in the _Flying Mermaid_, are told
of in the third volume, entitled "Five Thousand Miles Underground." The
_Mermaid_ could sail on the water, or float in the air like a balloon.
In this craft the travellers descended into the centre of the earth,
and had many wonderful adventures. They nearly lost their lives, and
had to escape, after running through danger of the spouting water,
leaving their craft behind.