Lord Hastings raised his voice and shouted after them.

"I'll wait here until you return. Don't be gone any longer than you can help."

"We'll be back within the time I mentioned," Captain Nicholson called back.

Lord Hastings signified that he was satisfied, and waved his hand to the departing boat.

Jack and Frank waved in return.

CHAPTER XXIV

UNDER THE SEA AGAIN

"I have not yet told the men what I propose to do," Captain Nicholson informed the boys, a.s.s they made their way aboard the Y-3.

Captain Nicholson introduced the lads to the man at the helm.

"Old Jansen," he said with a flourish of his arm.

The boys acknowledged this introduction, and Old Jansen touched his cap.

"Jansen," said the commander, "we are going to attack the Turkish battleships at the mouth of the Euphrates."

The old man let out a siren-like yell, and turned crimson all over his pink and white face.

Captain Nicholson turned the submarine over to him, and, followed by the two lads, made his way below.

"I never knew eighteen throats could make so much noise," said Frank to Jack, after the crew had been informed of their project.

And it was indeed a terrific noise the men made when they learned they were about to go into action.

"The 'subs' aren't like the big ships," Captain Nicholson explained. "With such a small crew I know the men personally, and I know I can count on each and every one of them, particularly Old Jansen, and Brown, the gunner's mate. I need not caution the engine-room crew for special watchfulness. Every oiler aft knows a warm bearing would condemn him forever in the eyes of his shipmates."

A few moments more and the submarine was racing along toward the mouth of the Euphrates, where the enemy was known to be. Just as dusk was setting in, Brown, the gunner's mate, reported an aeroplane to leeward. Captain Nicholson, Jack and Frank, who stood on the bridge, could just make it out with binoculars.

"I hate to use any electricity out of my batteries now," said Captain Nicholson, "for it is likely to be very precious later.

However, I don't want to run chances of being discovered. We'll dive."

The three made their way below. The entrance was hermetically closed, and soon the tanks were being filled. A moment later the Y-3 began to submerge.

At a depth of 60 feet Captain Nicholson trimmed down, and f or an hour the vessel ran along at eight knots, the commander wishing to make sure of complete darkness before coming up.

"How do you manage to keep your course under water, captain?"

asked Frank.

"Simple," was the reply. "Gyroscopic compa.s.s."

At that moment the man on watch at the bell receiver reported the sound of a ship's propellers above. Captain Nicholson turned his place at the periscope over to his first officer and listened himself.

The steady rhythmic beat was well off the port bow.

At Captain Nicholson's command, the main ballast tank was emptied until the conning tower was well awash. Then the commander, Frank and Jack went up to have a look around, for the airship, as well as for the vessel.

"Those sky pilots," said the commander, "maintain that they can see us and get us with bombs at any depth. However, I see nothing of our friend. Looks like he had lost his bet this time."

They returned below, and Frank put his eye to the periscope.

Almost instantly he made out the outline of large vessel of some kind. He reported this to Captain Nicholson, who brushed him quickly aside and peered into the periscope himself.

"Merchant vessel of some kind," he said aloud. "We haven't time to fool with him now. May be able to get him as we come back."

Once more now the three made their way to the bridge. The clouds had gradually thickened and it was very dark.

"I wish it would rain," mused Captain Nicholson, "or that we would at least have a dull sunrise, for it will be better suited for our work. Brown says he's sure we'll be favored with suitable weather because of the righteousness of our cause; but I am pinning my faith to the barometer, which has already fallen two points."

"Well, I hope everything goes all right," said Jack.

"It will," said the commander grimly. "You can bank on that, son. Might as well give the men a little rest," he added.

He poked his head down and called out:

"Turn in and pipe down!"

Then the commander and the two lads stood watch on the bridge.

At 2 o'clock, according to the captain's reckoning, the submarine was well off the mouth of the Euphrates.

"Can we find our way in by the navigation lights?" asked Frank.

"Not much," replied Captain Nicholson. "We'll stand off and on near where I place the sh.o.r.e line till we have daylight enough to see what we are about. Anyhow, I don't suppose there will be any lights, or if there are, they will likely be misplaced, to lure somebody to death."

Now the commander went below and bent over the charts for perhaps the hundredth time.

"About two miles off yet!" he muttered.

The chart gave the bottom on the sandbar in front of the entrance as sh.e.l.l and hard sand.

"Lucky," Captain Nicholson told the boys when he returned to the bridge. "This will allow us to run with very little under our keel in no fear of rocks."

"Is it very deep along here?" asked Jack.

"No," replied the commander. "That's what worries me. The chart shows a bare six and a half fathoms over the bar, continuing slightly deeper until it sheers off into the deep basin that is the inner harbor."

"And how much water does the Y-3 draw?"' asked Frank.