"There are two vessels about five knots a little south of west from here. One is probably a convoy."
"Run about three knots closer and take another peep," the captain ordered. "Did 17 and the 23 sight them also?"
"I think so. Seventeen just went under."
Irving understood this question and answer to refer to two other U-boats that accompanied No. 31 on this trip. Meanwhile the latter submerged to the depth ordered by Lieut. Voltz.
Twenty minutes later the periscope was again a few feet out of the water with the lieutenant's eye glued to the glass and his right hand working the lever.
"Let me have a look," said the commander.
He gazed a minute into the glass and then said:
"I'm going to try to get that convoy first and then the other, which appears to be a hospital ship."
Irving shuddered.
The order was again given to submerge. The lieutenant seemed to be doing all the work of lookout, pilot and operating master, for he was busy at the steering wheel, periscope, and speaking tube almost simultaneously much of the time. All these were within easy reach from one position. The "sub" arose several times near enough to the surface to enable the lieutenant or the captain to take a peep at the prospective prey, and then down again it would go. At last, under direction from the captain, the lieutenant gave this order through the speaking tube: