sentences:  In order that his presence should not be detected Lt Barry lowered his periscope for a few minutes but at 0443 "D4"′s periscope was raised to reveal "UB-72" steering an easterly course.A few minutes later "UB-72" was on the British boat's port side and Barry waited until the U-boat came on to his sights.At 0450 Lt Barry fired a torpedo 600 yards (549 meters) from the target and after lowering the periscope for a few moments he released a second one.