"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 shore 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 shell 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. "From the top of her periscope to the bottom of her keel," replied Captain Nicholson, "the Y-3 displaces exactly 20 feet. It will be ticklish work to navigate in those six and a half fathoms (39 feet) without being drawn down by suction and striking bottom so hard as to rebound up to the surface, where the Turks are sure to see us." At 4:30 o'clock in the morning there was light enough to make out the small gray fort guarding the entrance to the Euphrates. The submarine did not lie more than a mile away. "It's up to us to get out of sight before the fort watchers see us," said Captain Nicholson. Being satisfied of how far his run should be and verifying his course by the compass while still on the surface, Captain Nicholson quickly ordered the vessel trimmed down to a depth of 60 feet, and then started forward at about four knots--as low a speed as was consistent with good handling. "Lucky it's high tide; just beginning to ebb," said Captain Nicholson. "We'll find all the water on the bar that is ever there." There was to be no more sleep now on the Y-3. From the gunner's mate down every man of the crew was on the qui vive. As the submarine neared where the bar was charted, it came up till the pressure gauge showed only ten feet of water above. "Ten feet to hide us from the forts' lookouts and guns," explained Captain Nicholson.