ehind him. The lad performed a similar service
for those in the rear. A sentry was approaching.

Mackinder sank upon the ground. Although the night was too dark for the
lads to see this action they were close enough to be aware of the
movement. Instantly all followed suit.

In a moment they breathed more freely. The sentry had passed within a few
paces of their position. Evidently his feeling of security in the
isolation of the island had made him somewhat negligent of his duties. He
proceeded against the storm with head bent low.

Again Mackinder rose to his feet. Cautiously he crept forward.

On tiptoe the party gained the shelter of the warehouse.

"Gee!" declared Jimmie as the edge of the wharf was gained, "I clean
forgot my kit! What shall we do?"

"Hush!" warned Ned. "Don't even dare think of your kit!"

"I should say not!" put in Harry. "Think of your head instead!"

"And the mines at the harbor entrance," added Frank.

"All right!" submissively agreed Jimmie. "I'll keep quiet!"

The wind had risen to such an extent that walking on the narrow planking
was not only uncertain but extremely dangerous. Mackinder solved the
problem by dropping to all fours. The boys followed suit.

Directly they gained the submarine, the hatch was placed quietly in
position for prompt closing and the lines which held the boat were let
go.

Owing to the movement of the boats caused by the roughened surface of the
harbor creakings and groanings of the fenders had served to drown any
noise the party had made in crossing the narrow bridge of planks.

Jimmie held the wheel as Ned gave the signal for casting off the lines. A
touch of Harry's hand on the lever started the engines. The submarine
began to move. Suddenly a loud splash alongside attracted the attention
of all. Frank came scuttling down the ladder.

"Now I've done it!" he gasped. "I forgot to shove the plank back onto the
next boat and it fell into the water as we started!"

"Wonder if the guard has heard it!" speculated Ned. "Let me up!"

Under protests from his companions the lad mounted the iron ladder and
thrust his head through the hatch.

"I hear someone running along the dock!" he announced presently. "I'll
bet they have heard that noise! I see a light!" he added.

"What are they doing?" inquired Jimmie, holding the boat directly in the
center of the channel as he peered anxiously ahead.

"A fellow with a lantern is running out along the planks," repli