nd made for the
locks of the subterranean canal, picking up Romehl at a preappointed
spot on the way.

* * * * *

The canal locks were unguarded, as well as the storerooms of the
submarines. Each of the rooms held two subs, and could open onto the
second lock and be separately flooded.

The submarines were of steel as thick as Abbot's bathysphere. Their
shape was that of an elongated rain drop, with fins. In the pointed
tip of their tails were motors which could operate at any pressure. At
the front end were quartz windows. In the top fin was an expanding
device which could be filled with buoyant gas, produced by chemicals,
when the craft neared the surface. Each submarine also contained a
radio set, so tuned as to be capable of opening and closing the
radio-controlled gates of the locks. Each would carry comfortably two
or three persons.

Having picked out two submarines and found them to be in order, Hakin
sneaked back into the corridor to set off the time-fuse, leaving his
three companions in the dark in the storeroom. Abbot put a protecting
arm around Milli, while Romehl snuggled close to her other side.

Their hearts were all racing madly with excitement, and this was
intensified when they heard Hakin talking with someone just outside
their door.

Then Hakin returned unexpectedly.

"Something terrible has happened!" he breathed. "The explosives have
been discovered and are gone. One of the expedition men has just
informed me. Someone must have gotten word to Thig--"

"Why, _I_ did," interrupted Milli. "I told my guard, just before they
came and changed him."

Abbot groaned.

Hakin continued hurriedly: "So Dolf plans to leave at once. He is
already rounding up his followers. Come on! We must get out ahead of
him!"

An uproar could be heard drawing near in the corridor outside. Abbot
opened the door and peered out; then shut it again and whispered, "The
two factions are fighting already."

"Then come on!" exclaimed Hakin.

* * * * *

As he spoke he turned on the lights, wedged the door tight against its
gaskets and threw the switch which started the water seeping into the
storeroom; then he led Romehl hurriedly to one of the two submarines,
while George and Milli rushed to the other. Heavy blows sounded
against the storeroom door.

The water rapidly rose about them, and the four friends crawled
inside the two machines and clamped the