Yarrow Boiler. Water-tube boiler consisting of two lower water drums and an upper steam drum, these being connected by water tubes. In the triangle thus formed is the furnace, which heats the water drums, tubes, and lower side of steam drum. Water level is about halfway up steam drum.
Yaw.To lurch, or swing, to either side of an intended course.
Yawl. Decked sailing boat having main mast and a small mizen mast that is abaft tiller. Sheet of mizen sail is led to block at end of a bumpkin clamped in fore and aft line at transom. 2. Original name of jolly boat of Royal Navy.
Year. Unit of time based on one revolution of Earth around Sun. It has varying values depending on point of definition used, and on mode employed. See Anomalistic, Bissextile, Civil, Equinoctial, Leap, Mean Solar, Sidereal, Solar, and Tropical years. The year in common use is the Civil Year.
Yellowed.* Old term applied to an officer of Royal Navy who had been informed that the Admiralty did not intend to further employ him.
Yellow Jack. Originally meant 'yellow fever'. Later, applied to the yellow flag flown by a vessel when in quarantine.