The Plymouth leaped ahead, as did her sister ships on either side.

"We're off," said Frank.

Away they sped in the darkness, a division of four Yankee destroyers,
tearing through the Irish sea on a rainy morning; Frank knew there were
four ships in line, but all he could see was his guide, a black smudge in
the darkness, a few ship lengths away on his port bow. Directly she was
blotted from sight by a rain squall.

"Running lights!" shouted Frank.

The lights flashed. Frank kept an eye forward. Directly he got a return
flash from the ship ahead, and then picked up her shape again.

Morning dawned and still the fleet sped on. Toward noon the weather
cleared. Officer and men kept their watches by regular turn during the
day. At sundown the four destroyers slowed down and circled around in a
slow column. The eyes of every officer watched the clock. They were
watching for something. Directly it came--a line of other ships,
transports filled with wounded soldiers returning to America. These must
be safely convoyed to a certain point beyond the submarine zone by the
Plymouth and her sister ships.

On came the transports camouflaged like zebras. The Plymouth and the other
destroyers fell into line on either side of the transports.

"Full speed ahead," was Captain Templeton's signal to the engine room.

"Take a look below, Frank," said Jack to his first officer.

"Aye, aye, sir."

Frank descended a manhole in the deck. He closed the cover and secured it
behind him. At the foot of the ladder was a locked door. As it opened,
came a pressure on Frank's ear drums like the air-lock of a caisson.
Frank threaded his way amid pumps and feed water heaters and descended
still further to the furnace level.

Twenty-five knots--twenty-eight land miles an hour--was the speed of the
Plymouth at that moment. It was good going.

Below, instead of dust, heat, the clatter of shovels, grimy, sweating
fireman, such as the thought of the furnace room of a ship of war calls to
the mind of the landsman, a watertender stood calmly watching the glow of
oil jets feeding the furnace fire. Now and then he cast an eye to the
gauge glasses. The vibration of the hull and the hum of the blower were
the only sounds below.

For the motive power of the Plymouth was not furnished by coal. Rather, it
was oil--crude petroleum--that drove the vessel along. And though oil has
its advantage over coal, it has its disadvantages as well. It was Frank's